I've been running DOFF missions pretty constantly for the dilithium (doesn't give much but every little bit helps), and I've run into an unusual problem that I haven't seen before. I can't collect the rewards on the last mission left in the "completed assignment" list. I always have one mission sitting there that I simply cannot collect my rewards from.
I can be patient and wait for a fix, but I thought I should at least let you know.
Things to check for:
1) The mission is awarding you DOFF(s), and you don't have room in your roster
2) The mission is awarding you Prisoner(s), and you don't have room in your brig
3) The mission is awarding you item(s), and you don't have room in your inventory
Usually, if this is the case, you will get a red message across the middle of your screen when you try to collect the rewards. Just wait for the old messages to clear out, then try collecting the reward again.
My guess dil reward is a special transaction with a game server. And game server being laggy as god knows what, and generally screwed in every other way. So there's a delay for that dil granting transaction and another transaction updating your doff mission list. Sometimes it's just takes forever, or server did not process it at all.
It normally takes me 5 clicks to activate single copy of TT in battle, because of the same lag issues, and here you are complaining about doff assignments