Win10 2016 Multiple Monitor Orientation Display Issue

[PRDIT]

I have a Win10 Enterprise Edition 2016 PC connected to two TVs. It replaces a Win7 Enteprise Edition TV that was connected to the same TVs in the same orientation. The TVs are each in portrait orientation with their top bezels touching (to minimize gap between the screens), so the left (primary) screen is in "Portrait" mode and the right (secondary) screen is in "Portrait (flipped)" mode. UltraVNC is set to show the secondary display.

When the PC is not logged in, the screens display properly, but when it is logged in, the resolution of the VNC window and mouse location are each correct, but after displaying correctly for a brief period (seconds at most [after login or reconnect from UVNC]), the pictures turn sideways and overlap each other at the top of the window instead of being in the proper orientation and correct portion of the window.

I can not state for certain that this issue is or isn't version or configuration specific, because I'm not sure what version was installed on the Win7 machine, but I can state that I am using version 1.2.1.2 in when I see this issue. I can also state that I don't see this issue when using the same version and configuration on other Win10 Enterprise Edition 2016 PCs where there are multiple displays with higher resolutions that are not rotated.

Restarting the service or the PC does not change the behavior. Any suggestions on what I can do to try to resolve this?

ETA: Sorry for the duplicate (now deleted) post, missed the moderation notice and thought I had answered the spam blocker wrong.

[PRDIT]

I was able to resolve this by disabling the "Use system hookdll" setting. When that setting is on, the problem seems to occur regardless of several other settings on the "Screen Capture" tab. If this needs to be reported as a bug or additional information needs to be collected, I would be happy to try to help out if someone could point me in the right direction.

[scholar80]

PRDIT, thank you for posting this issue and a fix. I registered just to post this.

I too have this issue: Win10 Pro, 3 monitors (portrait orientation). Again, the "Select Full Desktop" option yields a perfect reproduction for about 2 seconds. After that, it seems that the secondary displays are cropped, rotated, and overlapped onto the primary display. Only the display is a problem, as the mouse pointer movement is reproduced perfectly.

If this is a bug, I hope it is resolved in the future. Until then, thanks again for the fix.