Situating: After installing Windows 10 version 2004, the user gets BSOD: RDR_FILE_SYSTEM.
Resolution:
Scanning the web religiously I found a reference which suggested the problem was in the mrxsmb20.sys file itself, that it was being overwhelmed. Several people suggested downloading a copy from another system of the file and bringing it over (tried, major permissions struggle but do-able), it failed. But one guy in the middle of a long string of diagnisis and suggestions suggested
Disabling offline file synchronization.
