Up until recently, the following has always worked.
ISE, tac cube, I'm in tactical mode, as I have been since the start of the match. I attack the tac cube, bring down a facing, and then use plasma lotus. Plasma lotus goes into cooldown, and then I switch to defensive mode and use tachyon inversion beams. Mode changing goes into a 20 second cooldown, after which I change back to tactical mode and continue firing until the cube is dead.
What's been happening over the last few matches is that after firing the plasma lotus I try to switch to defensive mode and I hear the audio for the switch but nothing happens. No ship animation. No mode switch cooldown. No availability of tachyon inversion beams.
The last time it happened I sat there for a couple minutes (still in ISE after it was over) periodically pressing the mode change button. I heard the sound for it every time, but no animation, no mode change, no change to power, no icon change. I was stuck in tactical mode.
After leaving the match I went to ESD system space and toggled the mode change button back and forth and it worked normally. Plasma lotus was still on cooldown for some of these toggles.
Not sure what's up. As far as I can remember this change happened in the last week or so, NOT when I first upgraded to the Fleet Daeinos, which was several weeks ago.
To complicate matters I did another ISE and everything worked normally. After more playing around and intently listening to the sound effect for the mode change, I'm almost positive that when the mode was bugged (and stuck on tactical), the sound effect that played repeatedly was the effect for changing to tactical, not reverting to regenerative mode.
Will try to get more details if I run across this again.