Strange behavior when connected

[FFranta]

Hello,
We installed Veyon (4.1.2) in our classroom (25 PCs - Win10 PRO, Intel Pentium G4600, integrated graphics Intel HD 630, 8 GB DDR4, in domain) in September, but nobody used it since last week.
Last week I started my teaching career and wanted to start using the software, but a problem occured.
As soon as I launch the Veyon Master on Teachers PC, thumbnails of all the clients PC monitors appear, bud then all the clients PCs and even the teacher`s PC start acting really "weird":
For example, I have 2 windows open - Google Chrome (top) and Mozilla Firefox (in background). When I try to minimize the Chrome, it doesnt minimize but stay in top. But if I click at (not minimized) chrome, it actually clicks to the Firefox (hidden between the Chrome).
Hard to describe, I tried to make a video: [https://www.youtube.com/watch?v=JG8IRZeDeaA](link url)
For example, at time 0:40 I click (open) firefox (you can hear the "click"), but the window doesnt appear. Hoewer, at 0:46 i mark a text and move a picture in the firefox window, which eventually appears at 0:49 (text already marked).
Another example - at 1:19 i minimze Chrome (but it doesnt disappear) and when I at 1:31 - 1:41 keep clicking to the Chrome, it actually clicks to the Firefox in background. And vice versa at 1:48. Again in 2:01.
As soon as I close Veyon Master, everything start to act normally.
I tried upgrade Teacher PC (with master) and a few clients to latest ver4.1.7, but i didnt help.
Could you please help me - what could I try to figure out the problem?
Thank you VERY much.

FFranta
Czech Republic.

[FFranta]

I tried to upgrade graphics driver, didnt help. After upgrading Veyon to 4.2 Alpha (4.1.91), the problem is solved and everything works fine. Thank you.