Check this Alex (With cudatext-win-x64-1.132.9.0b)

the same build, without lexers at game…
not always, but that repainting issues can see also on current official build - sure, will be enough to correct it at upcoming releases
unfortunately - I have not exact steps to simulate it, looks to me like random, not always…
moved second report to #3350 .
I have the repro (even without drag-drop). working in it.
found the reason! made a fix (for multi-tabs work-- drag-drop was not the reason). updated!
@Miroslavmatas pls check it, maybe your issue is also fixed
I am away from home. In a couple of hours, I'll be back.
UPDATE:
Working well. The other issue when the same file is opened by another application commented in #3338, seems is ok too.