Unable to upgrade to Big Sur 11.1

After completing the download and about 10 minutes in the prepare stage, the installer fails saying something went wrong with the download. (Which means it unnecessarily restarts the download when I try again, but okay.)

From the system console I got this which looks like a hint:

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[UpdateAttemptFailed] SUCoreUpdate update attempt failed with error: Error Domain=MobileSoftwareUpdateErrorDomain Code=44 "bridgeOS personalization failed" UserInfo={target_update=20C69, NSLocalizedDescription=bridgeOS personalization failed, NSUnderlyingError=0x7fc127df7630 {Error Domain=OSPErrorDomain Code=201 "An error occurred during personalization." UserInfo={NSLocalizedDescription=An error occurred during personalization., NSUnderlyingError=0x7fc127d14080 {Error Domain=AuthInstallErrorDomain Code=11 "(null)"}}}}

I hope you're not breaking your own firmware here.

My device: 2019 MBP 16", 2.6 GHz 6-core i7 with Radeon 5300M. Running Big Sur 11.0.1.
Update: already gotten two kernel panics the past few days. Investigating at the one from just now, looks like it's caused by a page fault in BridgeOS.

EDIT: Ah no, the "Problem report for macOS" looks to be pointing at Firefox?

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Process name corresponding to current thread: firefox

Unable to upgrade to Big Sur 11.1
 
 
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