Applying new maintenance to the Database Management Solutions for Db2 for z/OS r20 base install that had previously applied maintenance results in 55 PTF's showing "Applied in Error".
The cause of the PTFs in error was due to the ZFS file system not being mounted or incorrectly mounted.
The following message on the apply was the cause: /xxxxxx/xxxxx/PDTAAMKD: /xxxxx/xxxxxx/PDTAAMKD: not found
Correctly mounting the CDBAZFS file system and ensuring the CINSHFS and CSQ2HFS DDDEFs pointed to the correct USS directory allowed for the subsequent apply to succeed.