Ok, everyone know the problems about exchange, duty and other things related with season 6. I am not a member of the devs or staff of Crypt or PW, but I think an user, a theory about the exchange and duty problems. I can be really, really wrong and because this don't take any part of my text a official explanation. Is just a theory. A theory from a player like yours.
The exchange/duty/bank lag or problems is relate with "synchronization", how work the flags in an game item and how to work the item filters
Everytime you begin a Duty Missiom, place something in the exchange in the ESD or Qo'nos, buy something in the exchange, send a mail to someone, your actions are synchronized with the server, to send the response some moments later.
About the Exchange problem: Because the great amount of lag and a problem with the filter, the S6 and the past seasons items have problems to be placed well in the exchange.
The Exchange read your request to sell an item, but for an unknow reason to user, the exchange system not handle well the request, because something related with the flag of the item (ex: Weapon, pistol, consumable, lock box, etc).
Because this, the system try to handle with the request, but many times place an "invisible" item in the exchange, you can see in your sell window, but the exchange system can't show correctly in the buy window.
If you try to search, the exchange filter try to find your item under the filter sethings: If you want a very rare pistol MK XI, you have to set the filter "Very rare" quality, "personal weapon" as item filther and place "MK XI" or other word in the text search line.
In most cases, you find the item easily, but because the S6 new items and tags, you can't find correcty your items because or the items tags are outdated or/and the filter are wrong by some reason. And because this, the exchange system try to find the item with the wrong tools, making lag and probably some errors.
Because this, in the sell windows in the exchange, the system "frozen" your items, not showing in the sell windows or forcing you to wait some time, to server make the synchronization with your request and the sell windows, showing your last items.
If you place an item in the ESD and can't remove, is probably because something wrong in the exchange system to check the tag and handle with your request. But if you go to FED Academy or DS9 Exchange, you can remove and with some good luck, look to your items.
The same thing is related with buying in the exchange. If you have problems to buy something in the exchange in the Tuffly or in the Granalda starbase (KDF), go to Dronaza and you can buy the same item with some luck.
The reason is because a good amount of lag with the exchange console A to exchange console B, and if you are quick, can buy the same item two times, because the server have problems to synchronize your request in the exchange console A, but you can see the same item in the exchange console B, and in most time you can take "Unable to buy, try later", because the server see the exchange item already take by one player, but in a different exchange console, the request take some seconds to whole minutes to be executed in the system, giving lots of errors messages, or make some of your items in the exchange become invisible to you, or you can't find an item in the search because the synchronization and the filters are working wrongly for some reason.
As player, you have to wait the Devs finish the patch to correct this problem, but you can do this:
1 - If you have an item "frozen" in the exchange, go to another starbase or exchange console in a different map and try to remove your item. This can help.
2 - If you item are invisible but listed in the selling list in your exchange sell windows. showing only the number but not the item detail, name or other information, do this: Remove anything you can and place items with a price low, in comparative with your frozen item. This can force your item to show correctly in the exchange sell window. If you see, you can remove now or if the synchronization are really worse, just go to another exchange console in a different map and recover your frozen item.
3 - If you can't find anything in the search windows in the exchange buy windows, try to filter your search better. Duty can be checked easily, because they have a good and functional filter. But a lot of S6 items have problems with the exchange items, and you have to improvise.
Try "Reward pack" to most items of S6, because they are placed inside of a reward box, you have to open to be bounded to you. As ship, armor or weapon inside of a reward pack can be found easily in the right filter.
Avoid the "all" Filter for any cost. This don't work because have to check every item in the exchange database, generating a lot of lag handling with your request. If you can't know how to filter, try to place the direct name or a more unique partial word. But a lot of S6 items have problems with the flags to be reconize with the search of exchange.
4 - synchronization: If you have problems to do something, be calm and do later. The server have a lot of requests and places like ESD, DS9 or Drozana are the first place the people go to trade something. Try to visit an alternative place, like tuffli, D'kora, your starbase (if have to use only bank), other instance, like you are in the dronanza #1 go to dronanza #2 or try another time, a little later.
Because the synchronization problems, you have to wait some seconds to whole minutes to the bank, duty or exchange system handle with your request.
And because this, sometimes your request can't be accept (like placing a item in the bank or begin a duty mission) or in the moment is really worse and you can duplicate a duty mission (only give a fail message), place in a wrong way an item in the exchange, making invisible to search and/both invisible to your sell list in the exchange. Or if you are really unluck.
Handling with items in the S6 are forcing the system to deal with a good amount of lag and probably errors.
I am not a member of the devs or have any relation with the staff, and this is the best non-official explanation I can give with the vision of an user with some experience with games and programing. I can be really wrong in my explanation because is only an vision of a player, not a staff member. Don't take my text as oficial asnwer for your questions. Bran and the others members of the staff can do this in the right time, giving a patch note or explaning better anything.
Because no one of the staff are giving a better explanation and orientation in this moment, everyone are asking for patch and corrections, sometimes the Dev team can't give the proper answer because are to busy checking and making tests and for this reason can't place a word about this in the moment.
Try to wait a little and try again to handle with your items in the bank, duty or exchange or try to do your things in a different console, better in other map or instance. Less people, better synchronization with you and the server.