I backed up all of my data and reset the phone to factory defaults.
Before resetting the phone, I removed my MicroSD because the dialog said that it would delete everything on the MicroSD if I did not do this.
Sussing out the source of the problem:
After reformatting my phone, I slowly installed each app that I thought might be the ...
No, not possible even with root. And rightly so, since accessing fingerprint data is a huge security risk.
Android stores fingerprint data in Trusted Execution Environment and can't be accessed even with root. This data doesn't leave the device nor is it a part of app data. For more details, see key points related to the question
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