Question Portrait Mode Instability

[bullbearish]

Just built a new system and it runs great in landscape mode. When I switch a monitor to portrait mode I get reboots. I've logged CPU temp and it never gets over 40C. I'm not gaming on the machine. I'm using it for business only to monitor stock watchlists via Firefox. The monitors are old, reliable monitors I've had for quite some time.

Anyone with a similar experience / solution ideas?

System is:

MSI MPG Z390 Gaming Plus
Intel 9400F
MSI GTX 1660 OC 6G
Corsair 2133 memory
Samsung 970 EVO

 

[Ralston18]

Update your post to include full system hardware specs and OS.

Make and model monitors?

How do you switch the monitors from landscape to portrait? E.g., monitor menu, GPU control panel, stock market app, third party utility software?