With A/T engaged and F/D's on, pilot must follow the F/D or A/T may give adverse commands to FADEC. To avoid this situation, turn off FD's when not following their commands.
I.E., A/T and F/D's engaged and FCU ALT calling for descent. Pilot is fflying manually and decides to manually level-off without resetting FCU ALT that has open descent selected. A/T is calling for idle thrust to meet open descent command as well as F/D calling for nose down.
However, disregarding their commands, Pilot deciseds to manually level-off. Airspeed will continue to bleed off until Low Speed prot engages.
During RA resolution, chances are you are not going reset FCU commands before manually complying with RA command. Same situation as earlier, A/T will compensate to meet FCU ALT and F/D commands. Which may be the exact opposite of what you desire. So turn off F/D's so A/T revert to SRS sensing and commands.
Doesn't matter if you can fly "through" the F/D commands, what matters is what the F/D's are telling FADEC. If you want to manually fly and disregard the F/D's, then select A/T off any gu manual with the P/L's.
This is one of several posibilities, but message is the same....follow F/D's or turn them off.