Inaudible parts in audio edit mode (web version; MS Edge)

For the third day I have problems with editing the sentence audio in lesson edit mode.
When I click on a sentence and then listen to the audio (to match the timing) the first second is not audible. That doesn’t sound much, but up to five words are inaudible. When I replay the whole sentence, the audio starts correctly. This seems to happen when YouTube is the lesson source.
[My internet connection is not the reason.]

Edit: In reader sentence mode each saved audio works perfectly.

Thanks for reporting, we will investigate this.

Hi, today it’s working normally again!

Similar problem for me, but with an imported audio (mp3) for matching an epub.
In edit mode it worked fine up to a sentence, after that one, no audio was played for the remaining sentences and couldn’t sync them.
I tried to wait a while, log out and log in again but no change.
Playing the audio from the reader works fine.

@FrancescoLittarru Please post a lesson URL. Thanks.

Hi! The lesson is private and I can’t post it publicly.
Would it be ok to send you the mp3 and the epub somehow? I would add some notes to help you reproduce the errors.

Out of curiosity I re-generated the .mp3 from .opus (the original) with another program (Tenacity) and loaded the new mp3 in the lesson, now the editor works as expected!
It was probably a bad file that still worked well enough to hide its problem.
@zoran thank you for the support anyway.