Scratch all of the above. Just manually set the fan to 75%.

Issue seems to be resolved with the following steps:

-Perform a hard reset on the machine (using the reset button) after accessible through IP GUI.
-Flash to latest firmware for L3+ (https://shop.bitmain.com/support.htm?pid=0072017042706354248975UNDh65062D)

Edit: After the firmware flash, you should probably reboot the machine again. You might also try manually setting the fan percentage to 75%.

I'm having the same issue on 17 of my 180 L3+. It would make sense that a failure to read temp data would cause the miner to stop hashing (to prevent from burning boards). If it's a firmware issue, all of them should throw the same error in the kernel log - right?