I've recently been getting this in my UI after the most recent update. I've tried to clear the cookies and cache but that didn't seem to help. Each tab has the same issue, filled with rubbish.
Looks like some kind of log output.
Unfortunately you deleted the template and didn't post the information we need to help you
(Please remember to attach the systeminfo bundle)
What is the problem?
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What did you already try to solve it?
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Have you tried running in safe mode?
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Did running in safe mode solve the problem?
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Systeminfo Bundle
You can download this in OctoPrint's System Information dialog ... no bundle, no support!)
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Additional information about your setup
OctoPrint version, OctoPi version, printer, firmware, browser, operating system, ... as much data as possible
I'm quite impressed that your server still works at all, but it looks like you've got some kind of corruption going on there.
To fix OctoPrint, you could try reinstalling the update:
However, I would take it as a sign that your SD card may be dying. Keep regular backups to avoid data loss, and maybe look at swapping it for a different one.