Xorg hangs when using basic mosaic with two Quadro NVS 295 cards and 3 monitors

I have 2 Quadro NVS 295 cards on machine running CentOS 7 (gnome 3) and until recently I had just 2 monitors connected to just one of the cards. Everything was running smoothly (with driver version 340.101).

Recently I got another monitor and connected it to the second (unused until then) Quadro NVS 295 card to have a total of 3 monitor. In order to have all three monitors displaying the same x screen I enabled “Base Mosaic” in nvidia-settings, saved the x config file and restarted to have it kick in.

After the restart I got the login screen and all 3 monitors were on and seemed to display properly.

The problem:
After logging in (gnome 3) whenever a window is maximized (chrome especially) or increased in size sufficiently (taking up more than about a quarter of the screen surface) Xorg hangs (100% cpu usage in htop) for a few minutes.

dmesg shows that there are a couple of XID errors, XID 13 and XID 69.

If I turn Base Mosaic back off and use just 2 monitors from one of the cards, the problem goes away.
nvidia-bug-report.log.gz (191 KB)