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I have no idea what causes it, but my EEPROM settings have reset back to 'factory defaults' yet again. Last time it happened was a couple of weeks ago. The time printing and filament used get reset back to 0 and I have to re-calibrate axis and PIDs. This time I've taken a backup, but it would be interesting to know why this might be happening. I have not changed the firmware or anything obvious like that. I don't really have any stpes to reproduce the problem - it just seems to happen at random and not at all often.

This is a Max v2, latest repetier firmware (0.91).

One thing that I can think of is an unstable power supply which at random times would experience a voltage drop significant enough to effect your EEPROM.
Reading through the Forums you have probably found many threads that say the stock power supply is unstable and should be replaced with a larger power supply.

Insufficient power would not cause the EEPROM to be erased.
I can't think of anything off the top of my head that would cause this. Host software could do it.
What host software are you using?

Eons ago I had a similar thing happen with a new RAMBo I installed. Long story short, I scrutinized the board with a magnifier and found a solder bridge that had been manually worked to cut it. But, the cut was not terribly clean. It looked open but it was suspect. i cleaned it up and never had the problem again. Is this a new V2?

This is a new v2. Host software being used is matter control and occasionally repetier host. Looks like I better pull the board and have a good long look.

Also, now that you mention it, I have had a few shutdowns, but they were around accessing the SD card when I had first built the printer. I've not had any repeats of the shutdowns recently and have printed via both the SD card as well as over USB. I haven't noticed any shutdowns due to PSU load, although replacing the PSU is close to the top of my list - the stock 600W PSU just seems to be working.

I think a faulty Rambo sounds reasonably likely - issue is tracking down the fault now.

I have lost my z height and number of hours printed twice this month, using matter control. It might happen if I switch between repeater and mc , or it might also have happened when my USB connection went wonky. The USB connection seemed to get bad when I was trying to change temps from mc after i already hit the start button (play button in mc), something the mc people tell me that it won't work.
I just have to recal my z to get it happy again.

Thanks Tonkabot, that is also a possibility - perhaps even more likely as the Rambo seems to behave perfectly 99.9% of the time. I don't remember performing that sequence of operations, but I did very likely mess around with preheat and manual stepper controls in MC along with USB connects and disconnects.

Had another EEPROM reset this evening - but that was caused by a power cut. It looks like the repetier firmware is a bit sensitve to things like power cuts and resets the eeprom for no good reason. Oh, this was during a print.

I have the same problem. I start my printer and all is good but if i start the printjob, he start to print 20cm over the bed. Thats the point i know "he lost his settings"
horizontal radius, pid and z height <- all default values

i didnt think its the psu because i changed to corsair rm750