Background flash since 6.0.0. beta version

[11mail22]

Since 6.0.0 beta version I observed background flashes during same page is loaded.
This was not the case in 6.0.0. nightly versions and is not very comfortable.

I captured the behavior as video.
Pressing the Return button which generate a http request with same page.

beta2 version

same with
nightly version

Web Theme is force dark. When switched to light mode, background is flashed white.

[11mail22]

After install nightly and reinstall beta2 with restore settings, background flash is gone.
So, I guess, no bug.