This is not a big problem, but I wonder if others have it too or if it could be an indication something else is wrong.
When I use the LCD to move the Z axis and I turn the knob fast to get the platform down >50mm, the firmware reboots.
If I turn the button slow enough, or use the PC/raspberry to control the Z axis, there is no problem.
It doesnt seem to do this on other axis, but I havent tried exhaustively.
Yes, I remember this happening once in the early days (ie early 2015), so I was always careful after that. I tried again from the LCD knob and later used Repetier, S3D or Octoprint for controlling axes, as they supported larger increments anyway.
As you mentioned, it’s not a big issue, I should have mentioned it too probably but I had other learning-curve issues at that time 
John
This has been normal behavior before and after firmware update. Somewhere else on this forum is an explanation that the onboard controller has a buffer size for only so many commands, and spinning the encoder wheel can easily fill and overload that buffer for slow operations like 1mm movements. If you try hard enough, you can get it to do it on X and Y axis as well!
I’ve found the secret to much happiness with the Vertex is to remember the old joke: “Doctor, it hurts when I do this.” “Well, stop doing that!” So if a problem happens when you turn a dial too fast, the high-tech solution is to turn it slower. 
I thought it could be something like that. No big deal, and it would be even less of an issue if the controller allowed Z axis movements in 10mm increments.
Anyway, good to know Im not alone 