Hi Bluu This is not unexpected. You shake the FC and the sensors and the FC tries to correct the movement. Nothing wrong with RPM change. Experimenting with different standoffs is a good idea anyway to get rid of your logged bulbs. BTW did these bulbs occur while you where looging with your hexa fixed to the table or did you log inflight?
So maybe you do not change anything in your mountning the FC and take a log inflight. The FC does not like to tied down. The bulbs could easy come from tiedown.
Let us see a inflight log first. edit: or a hand - held - almost - free - hover if you dont feel like flying.