How many controllers do you have in your preset?
I have a few presets which are guaranteed to freeze the FM3 with CPU not hitting 80%. I've reported/shared them to Fractal, but apparently those are not fixable due to many controllers used. I use Pitch followers and Envelope followers quite extensively. Some of my presets are below 80% but 100% freeze a device after an attempt to switch a scene, etc.
It is also affecting scene switching speed - when such preset is processing the sound (i.e. guitar volume knob is not 0), the scenes will not switch until I'm muting the guitar - I believe this is due Pitch followers producing a high load on CPU blocking other actions to keep the sound flowing.
Also, FM3 freezes quite often when uploading an IR from Cab-Lab 4 to such preset - no issues with presets which are not close to 80% and have less controllers. So I work on IRs using simplified presets and them transfer them to the main presets. Keep this in mind just in case.
Try removing a few controllers like Pitch followers if you use them and see if stability improves. This works for me, but I keep running the device on the edge anyway, as I'm not gigging a lot these days and can wait for the reboot
The only bad thing is that my device sends a loud pop to the speakers when switching off and on, so when I'm plugged in directly into the speaker without volume control such as Genelec monitors, it brings some discomfort.
I'm rarely have any freeze issues with the presets over 80% if the controllers are not used.