I posted this somewhere else, but I forgot where, but I haven't seen anything mentioned about it yet.
When Season 5 rolled out, I did the mission to purchase Antiproton Turrets on a KDF toon. I did two of them. The first was a critical success, while the second was a normal success. I received absolutely no rewards for these missions - no turret, no CXP, nothing at all.
For other types of turrets, after they're deployed, they just seem to stop working at some point. I've dropped a couple to help defend the Kang in Cure Space. After the skirmish with the group of enemies I'm fighting when I drop the turret is over, the thing just sits there and lets anything else go right by it without firing a shot. It's like it goes into "non-combat" mode once the first fight is over and then doesn't feel like engaging other targets. However, even if the turret is attacked by something, it still doesn't shoot back.
And finally, to add something new to this mix, the turrets that are purchased still seem to be single items with 20 charges, whereas the crafted ones show up as a stack of 20 individual turrets.