Sequencer pause not pausing some char animations

We are trying to update our engine from 4.18 to 4.20 and we have some issues with the sequencer.
when playing sequences in the sequencer, and pausing, some characters keep playing their animations.

It seems that it’s linked to the way we start the play. If the scrub cursor is in the animation section, play and pause is good.
It the cursor is placed before the section then the pause inside the section doesn’t work.
The bug occurs into a sequence used as a sub sequence of another, maybe there is some link too…

Of course, we have made some modification in the game, using custom AnimationInstance, but it works in 4.18, so I assume is linked to the new time management introduced in the 4.19 or 4.20.

The problem is… i can’t find a way to debug the animation process… I don’t understand where the animation is computed.

Where can I break in C++ to find why in some case the animation is applied despite the pause.

If someone can help me, it can save me a lot of trouble…