Problem in exposure when exporting files from LRC

I'm facing a problem I never experienced in 12 years using LR ( then LRC)

When I export photos from Lightroom Classic, some exports have a different exposition than inside lightroom (usually underexposed). And it seems to be a random problem as some photos have it and some other don't, even when I synchronize the files from the ones that are doing fine.

I tried many things:

- export to photoshop

- convert to dng

- create a copy

- doing a completely diferent edit

- optimizing Lr Catalog

- export to a diferent catalog

- going back to previous versions of LRC

- deleting dynamic previews

But none are helping.

However, I found a way to avoid the problem,  I have to simply overexpose by +/- 2stops. But it is not easy when one has dozens files with this problem.

If anyone could help, it will be very appreciated.