I updated to RouterOS 6.43.1 from version 6.41, and now the fans keep spinning every few minutes constantly.
One thing I noticed is under "System --> Health" the switch seems to think the CPU is at 40C, when the CPU usage is at 0-1%, and the unit itself is very cool to the touch.
My home office where this switch is located is kept on A/C set to 71F (21.6C). It's fairly cool, nothing else is near it on my desk etc.
This only become an issue literally now after installing the update.
No other changes to config etc.