Unexpected error #10501 (SL1/SL1S)

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What happened?

The printer is displaying the message: "An unexpected error has occurred. If print job is in progress, it should be finished. You can turn the printer off by pressing the front power button. See the handbook to learn how to save a log file and send it to us."

Error name: Unexpected error 

Error code: #10501

This error is shown when the printer finds an unexpected error. If the error is shown during a print, the current job will be finished. You can turn the printer off by pressing the front power button.

How to fix it?

Flash the firmware to the latest version.

In case the issue persists, save the log file to a USB drive, or update the log to the Prusa Server as shown here: Saving log file (SL1/SL1S), and contact your support.