(moved from bug 6961, comment 7)
I can reproduce this problem
1. Started Thinlinc 4.12 client (Debian 10) to 4.12 server (Debian 10)
2. Opened up 'Master PDF Editor 5', then opened up a PDF
3. Go to Comments menu -> Stamp,
4. Select a Stamp, it crashes
The problem is that it changes the mouse cursor to a very large cursor which is a stamp that you use on your PDF. So this could happen in any program which changes the cursor to a large picture.
When this happens the user gets a dialog with:
> An unexpected error occurred when communicating with the server:
> Too big cursor
An you get this in tlclient.log:
> 2022-04-06T08:37:40: vncviewer[E]: CConn: Too big cursor
The current limit for the cursor is 256x256. It seems this is insufficient for some applications.
I'm not seeing any obvious limits in Xorg itself for cursor sizes, except that graphics drivers can state the largest cursor they can handle in hardware (falling back to software for cursors larger than that).