Cryptomatte Sequence skipping frames

Hi there, the following behaviour has happened to me a few times the last days.

I have an EXR Cryptomatte image sequence that works fine for the most part. The issue is that one specific frame shows black, as if the Cryptomatte effect is not affecting it.

File size of that spefic frame is correct and it opens in photoshop normally -via Exr-IO pluging etc.
AE, drivers, Windows and Mac (problem persists on both OS) are updated.

Things I've tried:

I imported that single frame -not as a sequence- and it works and acts fine (in fact I'm using this as the way to solve this issue, but it's a pain)

I have tried replacing that frame with another one from the sequence (copied and renamed) and the problem persists -so it's not the actual frame it seems.

Also tried with previous version of AE, problem persists.

Thanks in advance for any help