Fonctionnement DXO et fichiers "DOP"

Again, it depends on where you manage your metadata and keywords. I do it in Lightroom and switch autosync off in DPL as well as in Lightroom.
What you do, is up to you, main thing being: if you manage in “A”, switch sync off in “B”.

Syncing in “A” and “B” is the least desirable configuration imo, others might have other opinions though.

In which app have you added metadata so far? Lightroom or PhotoLab?

Well I would like to be able to do it in both, but from what you say it is better to do it in one.
In this case I’d rather take Lightroom because I’ve already had “weird” behaviour from DXO on metadata.

How can I adjust both software to have a correct reading of the modifications made?

Thanks for your help.

Stick to Lightroom for now and set PhotoLab to NOT sync metadata.

The “read metadata from file” command can be found in PhotoLab’s file menu. Metadata will be read from new files automatically, old files can manually be re-read when and as often you like.

Be sure to read the text in the preferences. Metadata can be in the file itself and in the xmp and dop sidecars.