Unanswered R1plus halts mid-print, light goes off, cools off after

I have been printing successfully on my Robo3Dr1+ with MatterControl 1.5 for years. Three days ago it quit printing mid print - a sudden halt followed by the light going out inside the housing. The fans were still on and it seemed like the connection was still active, but the controls on MatterControl stopped controlling the printer.

Everything is as it was out of the box - MatterControl, printer firmware, I haven't updated/upgraded any of it.

I tried to troubleshoot -
I tried a different print height/layer thickness to see if I was just bogging my nozzle. Same result.
I tried cleaning the hot end and channel just in case; it was clean, and I could extrude cleanly with no issue.
I read the forums after that and saw the suggestion to check the logs, so I ran it again and when it crashed I paused and grabbed the log. The crash happens, it looks like communication pauses (?) and then the temperature plummets. I will attach below.

The forums suggested behavior like this might be a USB glitch, so I tried a new cable; same result.
Then I tried a a new port on the computer; same result.
I Saved GCode to a SD card and loaded from that via MatterControl. Same result.
Thought the computer going to sleep or something might still be a factor, so I tried loading/starting via matter control and unplugged the USB from the printer completely; same result. It still printed for 15 minutes or so before crashing.

In every loggable instance, the temperature doesn't drop till the print has crashed, the issue isn't temperature. The issue isn't a clog in the hot end. It isn't a USB problem. I don't know what else to try. I'm open to ideas.

Here's the log grab. I think it stopped just before "communication state: Paused" but I grabbed from known-to-be-printing to the first word "error" that happened well after.

--------------------------------------------------------------

->N55797 G1 X145.74 Y123.07 Z2.4 E3214.636*10 [2798.106]
<-ok [2798.121]

->N55798 G1 X145.86 Y122.84 Z2.4 F9000*17 [2798.137]
<-ok [2798.153]

->N55799 G1 X144.89 Y123.81 Z2.4 E3214.704 F3900*101 [2798.168]
<-ok [2798.184]

->N55800 G1 X144.89 Y123.24 Z2.4 F9000*26 [2798.200]
<-ok [2798.215]

->N55801 G1 X145.86 Y122.27 Z2.4 E3214.773 F3900*104 [2798.231]
<-ok [2798.246]

->N55802 G1 X145.86 Y121.71 Z2.4 F9000*20 [2798.262]
<-ok [2798.278]

->N55803 G1 X144.89 Y122.67 Z2.4 E3214.841 F3900*110 [2798.293]
<-ok [2798.309]

->N55804 M105*43 [2798.324]
<-ok T:209.5 /210.0 B:51.2 /50.0 T0:209.5 /210.0 @:80 B@:127 [2798.340]

->N55805 G1 X144.89 Y122.11 Z2.4 F9000*24 [2798.356]
<-ok [2798.371]

->N55806 G1 X145.86 Y121.14 Z2.4 E3214.909 F3900*111 [2798.387]
<-ok [2798.403]

->N55807 G1 X145.86 Y120.58 Z2.4 F9000*27 [2798.418]
<-ok [2798.434]

->N55808 G1 X144.89 Y121.54 Z2.4 E3214.977 F3900*98 [2798.450]
<-ok [2798.481]

->N55809 G1 X144.89 Y120.98 Z2.4 F9000*23 [2798.496]
<-ok [2798.543]

->N55810 G1 X145.86 Y120.01 Z2.4 E3215.045 F3900*109 [2798.559]
<-ok [2798.622]

->N55811 G1 X145.86 Y119.45 Z2.4 F9000*26 [2798.637]
<-ok [2798.700]

->N55812 G1 X144.89 Y120.41 Z2.4 E3215.113 F3900*103 [2798.715]
<-ok [2798.762]

->Communication State: Paused

->M105

<-ok T:209.7 /210.0 B:52.5 /50.0 T0:209.7 /210.0 @:62 B@:0
->M105

<-ok T:209.1 /210.0 B:52.2 /50.0 T0:209.1 /210.0 @:78 B@:0
->M105

<-ok T:208.6 /210.0 B:51.8 /50.0 T0:208.6 /210.0 @:90 B@:0
->G91

<-ok
->G1 Y0.02 F3000

<-ok
->G90

<-ok
->M105

<-ok T:207.7 /210.0 B:51.4 /50.0 T0:207.7 /210.0 @:108 B@:0
->G91

<-ok
->G1 Y-0.02 F3000

<-ok
->G90

<-ok
->M105

<-ok T:207.0 /210.0 B:51.2 /50.0 T0:207.0 /210.0 @:119 B@:0
->M105

<-ok T:206.3 /210.0 B:50.9 /50.0 T0:206.3 /210.0 @:127 B@:0
->M105

<-ok T:205.0 /210.0 B:50.8 /50.0 T0:205.0 /210.0 @:127 B@:0
->M105

<-ok T:204.4 /210.0 B:50.7 /50.0 T0:204.4 /210.0 @:127 B@:0
->M105

<-ok T:203.5 /210.0 B:50.6 /50.0 T0:203.5 /210.0 @:127 B@:0
->M105

<-ok T:202.7 /210.0 B:50.5 /50.0 T0:202.7 /210.0 @:127 B@:0
->M105

<-ok T:201.7 /210.0 B:50.4 /50.0 T0:201.7 /210.0 @:127 B@:0
->M105

<-ok T:200.6 /210.0 B:50.2 /50.0 T0:200.6 /210.0 @:127 B@:0
->M105

<-ok T:199.5 /210.0 B:50.2 /50.0 T0:199.5 /210.0 @:127 B@:0
->M105

<-ok T:198.6 /210.0 B:50.1 /50.0 T0:198.6 /210.0 @:127 B@:0
->M105

<-ok T:197.7 /210.0 B:50.0 /50.0 T0:197.7 /210.0 @:127 B@:0
->M105

<-ok T:196.8 /210.0 B:50.0 /50.0 T0:196.8 /210.0 @:127 B@:0
->M105

<-ok T:195.3 /210.0 B:50.7 /50.0 T0:195.3 /210.0 @:127 B@:127
->M105

<-ok T:194.3 /210.0 B:51.8 /50.0 T0:194.3 /210.0 @:127 B@:127
->M105

<-ok T:193.6 /210.0 B:52.7 /50.0 T0:193.6 /210.0 @:127 B@:0
->M105

<-ok T:192.7 /210.0 B:52.3 /50.0 T0:192.7 /210.0 @:127 B@:0
->M105

<-ok T:191.8 /210.0 B:51.9 /50.0 T0:191.8 /210.0 @:127 B@:0
->M105

<-ok T:190.9 /210.0 B:51.6 /50.0 T0:190.9 /210.0 @:127 B@:0
<-Error:Extruder switched off. Temperature fell too much during print!
<-Errorrinter stopped due to errors. Fix the error and use M999 to restart. (Temperature is reset. Set it after restarting)

 

It occurs to me to wonder if MatterControl got tweaked somehow and is generating bad gCode. Failing any other more reasonable answer today I think I will try un- and re-installing MatterControl and see if I bungled the settings somehow. I don't recall doing anything, but I can't think of what else to try

 

In the interim here I have disassembled and cleaned the hot end, tried the print with ABS instead of PLA just because, and cleaned and lubricated all the moving parts.

We still end the same way.: a couple of clunks like it's trying to change directions or something, and then the lights go off and the machine stops.

The thing that's making me crazy (besides the "can't print" part) is the lights going off... the fans don't stop, the machine is still on, but it just ... stops. Is this a power supply issue? Is there something in the controller that could cause this? Is the printer just a paperweight now?

 

I have gone through and un- and re-connected everything I can. I've run a test print with a 10mm round by 25mm high cone and it printed fine, but I never did a small footprint before when troubleshooting, so it may not be a legit test. I'm running a test print on a larger piece now, we'll see what I get.

I will report back soon.

Thank you so much for the help.