NVDA reading every item in tab order

Hello all !

We have developed and used an accessible version of our storyline model for months. Everything was behaving as intended using NVDA (thanks for all the dev efforts regarding accessibility, by the way !) but we are now seeing a problem with accessibility and NVDA.

At the start of every slide, we have a home-made play button that, when clicked, changes state to become Masked, the slide launches and a pause button that was deactivated until then changes state to Normal.

The screen reader reads the alt text of the play button which is first in the tab order, and stops there (nothing abnormal here). When we click the button, it launches the animation and the voice reads the pause button alt text (as expected because of the tab order) but then the voice goes on to read EVERYTHING in the tab order on the base layer until it gets to the bottom of it without any user action. Then the screen reader goes back to the pause button where it should have stopped.

Strange thing : the screen reader shows this problem when the play button is click with the keyboard (Enter key or Space bar), but the mouse interaction works fine, the screen reader doesn't read beyond the pause button that appeared.

This problem seems fairly recent and appears when using Chrome 123.0.6312.86 and Edge 123.0.2420.65.
NVDA works as expected with Firefox.

Has this problem been flagged already ? It is a really big issue for us as every slide in the projects created in the last 5-6 months now exhibits this problem.

Thanks !