Ok, but the resolution of thumbs is saved IN the file, so with Autocad 2017 all my thumbs was in high resolution.

After installing Autocad 2019, the first things I noticed is that all my thumbs was in low resolution.

It's illogic, because I haven't open that files and I haven't resaved them with new version.

And now, if I want all my thumbs in hi  res again, I must open all my files and save them with THUMBSIZE > 5...?