This was born as a modified version of the default maximize kwin effect done to reduce glitches when using xrender backend.
Now xrender backend is gone, but sadly the bug is present with opengl backend due to the not-working anymore crossfade effect in kwin.

Related bug: https://bugs.kde.org/show_bug.cgi?id=418247
Video showing the problem (maybe watch it at reduced speed) https://www.youtube.com/watch?v=qKZE6icPHFo

You can install via Systemsettings (effects window).
...or manually:
* Download the archive
* extract the folder present in the tar.gz into your ~/.local/share/kwin/effects/
* from a terminal, start kbuildsycoca5 (or restart kwin, or relogin, or reboot)
* open the effect panel and disable the original maximize effect, enable maximize for xrender

*** BIG FAT WARNING ***
Disable the default kwin maximize effect, don't run them togheter.