today i found out (of course after painful hours of figuring out whats going on), that it seems to me, that the AimOffset node in Animation Blueprint has bug with sync groups. See the image below. If i used the AimOffset node (that uses the same additive animations, like below in the screenshot), my additive animations where not synced.
i tested this with setting the play rate to 0.1 and my animation in aim offset went really slow.
but when i my workaround it works nice like it should. my additive animation is following the locomotion group (walk run blendspace).
of course there is always the chance i messed something up or forgot to hit a button. so please let me know, if anyone has an idea.