I'm an experienced owner on my third Model S (late 2017 100D), and love the car, like the two before it. I know what's normal, and what's not, and how to deal with little oddities.
But I have to say that I have had MANY more MCU lockups and spontaneous reboots after getting firmware 2018.14.2 a88808e than I have ever had previously with any firmware version. I'd say I get spontaneous reboots three or four times per week, and a lockup every other day.
I've not called Tesla about this, but I am ready for a more stable firmware.