Screenres update quirks

[Emulog]

Help file states that a separate thread is created after screenres, and it updates visible viewport with current page.
Despite screen lock and unlock, this thread behaves badly.
Even if i run cpu heavy full screen update thousand times a second , using pointers, i need to do pset(0,0):pset(1023,767) before the test, and only then screenres updater act correctly.
If not use psets it will show only part of screen where print occured and no further.
And also if doing not full screen updates like a 256x256 window, psets do not even affect either.
Screen content seen only if i drag window outside a screen and then back.
So, fullscreen updates yet are visible, partial are not. IMHO its a bug.
Of course this "smart update" algo of that thread considered to be helpful, but why not just do a regular fullscreen update ?

[fxm]

A small example of code would be welcome.

[Emulog]

https://dropmefiles.com/PeaX1

Here is ready sample, just compile and uncomment lines to reproduce.
Relatively small. 100% acts with quirk on my PC.
Needs presupplied *.bin file to extract image data

My system is Windows 10/ Ryzen 5900HX, FB Version 1.09.0 as said in changelog.txt