This may be the issue. I sent a ticket to support, so hopefully they will address
I’d suggest connecting the printer directly to the AC power mains, bypassing your UPS and perform some tests.
Perhaps the UPS is causing an issue. Possibly it’s not supplying clean power (not sine wave), or it could have a problem with peak power, or it could be defective.
Okay I can try that but since it is a random event it may be hard to reproduce.
I do have the printer plugged into a WiFi plug into the UPS…so going directly to the wall will eliminate those variables, but it will stink to lose the WiFi power on/power-off capability
Yes the internal light was off too…if that makes a difference. This is why I felt it shutdown. So I pressed the button on my WiFi plug to get it to cycle on.
Check your amp rating on your WiFi plug some are only rated @ 10 amps max load.
Your house and UPS plugs are rated @ 15 amps.
I chrcked and it is 10amp and has overcurrent protection…
So you think that may be it? It isn’t happening atm on the prints I’m running but they haven’t been as long.
I can look for a 15amp one on Amazon if you think it’s a possibility
I have not personally checked the amp draw on the Bambu lab printer under full load @ 120 volts.
You also might want to look at the specs of your UPS to see how many watts it can handle if it is 1800 watts it would support a 15 amp load if your ac power source is 120 volts.
If this information posted on this link below is correct you can see it’s around a 9 amp at times if your voltage is @120 volts if your house voltage drops too much on the WiFi smart switch it can make the over current protection kick in and shut the power off to your printer.
Yes I would look for a 15 amp appliances smart switch it will have more over current room to work with with less fire risk.
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Thank you! I purchased a 15amp WiFi switch
My UPS 330watts …it is this one:
CyberPower CP550SLG Standby UPS System, 550VA/330W, 8 Outlets, Compact https://a.co/d/9uKFSDG
The ups has a 10 amp manual circuit breaker. I would only plug the printer and your small fan into it or you can overload it or trip the circuit breaker but this has not happened so we know you are not over the 10 amp spec.
The smart switches with the 10 amp rating and overcurrent protection circuits can be sensitive to voltage changes and loads.
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It’s not an AC power going away issue. You can confirm this for yourself. Turn the printer on and then unplug it and plug it back in. When you plug it back in, the printer will turn on immediately because the switch is still on. The OP’s printer turns off and stays off until he cycles power on the printer’s power switch. That’s not the AC power going away. That’s a circuit-breaker behavior.
WiFi controlled outlet - that could be shutting off due to overload. Easy to confirm. Remove the WiFi outlet from the circuit and plug the printer directly in to the wall. If it still shuts off, it wasn’t the WiFi outlet.
But I doubt it’s the outlet, either. If the outlet is overloaded and shuts off, the load goes away. If turning the printer on/off caused the WiFi outlet to “reset” (assuming it has some protection that’s tripping), the WiFi outlet should turn itself back on again as soon as it turns off. In both cases the load on the WiFi outlet is NIL, the outlet can’t tell if the printer is still present once its (theorized) circuit breaker trips. The described symptoms are not consistent with this being root cause.
I think it’s the printer’s power supply. But try running without the WiFi controlled outlet and see if that makes a difference. If it doesn’t, it’s the printer and not your AC that’s the issue. If it does, stop using the WiFi controlled outlet and reach around behind the printer to turn it on/off. 
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The way I read it is the op is talking about the manual on/off override switch on the smart switch not the printer power switch.
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I’m sorry, to be clear…when I said I power cycled it I meant I hit the button on the WiFi plug and it turned back on. I did not flip the power switch on the printer itself…So it seems conceivable to me that the WiFi switch was overloaded.
Also this happened once. It is not a common occurrence (yet)…. So I’m not sure how to test other than to run long petg prints and see if it happens again
Yes this is what I meant. I’m sorry if I wasn’t overly clear originally
Ah. In that case, the problem is definitely your WiFi switch. Why are you bothering? Just plug the printer in to the wall, problem solved!
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Yes that possibly will fix it. I introduced the WiFi switch recently figuring if I have a long print and I know it will end at 3am I can see a schedule to have it turn off the printer at 3:30
When the printer is idle, not printing, it draws about as much power as a lightbulb. Just let it sit until you wake up, and shut it off then. A few hours powered on but not printing is going to mean pennies to your electric bill.
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I had a UPS that shut down my resin printer. The UPS worked fine for a computer but it would randomly shut down the printer.
Did the UPS shutdown completely or just the single outlet? I assume it was the WiFi plug in my case as the UPS was still powering other things when it happened.
I did pickup a 15amp WiFi plug, however I haven’t done another long PETG print up test it yet.
The UPS was only connected to the printer. The UPS and the printer were powered up when I discovered the printer having been reset by a power off-on cycle.
Tonight my printer turned off and I finally understand what is happening…it’s not the printer turning off, nor is it the WiFi plug…
I have the printer plugged into a UPS on the protected side of the UPS. The UPS is rated 330W. The UPS protected side is turning off. I presume that the printer is drawing so much power that it triggers its protection circuit.
I’m plugging the printer into the unprotected side of the UPS (which didn’t power off). I’m fine with it not being on the protected side since the X1C does such a great job of resuming.