Last year my company read in excess of 20,000 tapes from just about every manufacturer and software vendor. For modern, LTO/3592/T10000 era tapes the failure rate we see is around 0.3%.
Most of these failures are due to:
cartridges being dropped or otherwise physically deformed such that they do not fit into the drives anymore.
cartridges getting stuck in drives and destructive extraction being required.
Data was never written correctly in the first place.
The only exception to this rule that we have seen is tapes written with LTFS. These tapes have a 20 fold higher incidence of failure, we believe because reading data back, as if it was a HDD, causes excessive wear.
Anyone claiming 50% failure rates on tapes has no idea what they are talking about, are reading back tapes from the 1970s/80s or have a vested interest in getting people away from tape storage.
They're not saying the failure rate of tapes is 50%. They're saying if you survey attempts to do data restores from tape then 50% of the time not all the requested data is found.
I can't claim the same volumes you can but I did handle tape backups and recovery for a mid sized business for a few years. We only had one tape failure in my tenure but we had plenty of failed recoveries. We had issues like the user not knowing the name and location of the missing file with enough detail to find it, or they changed the file 6 times in one day and they need version 3 and the backup system isn't that granular.
Those are just the issues after the system was set up and working well. Plenty of people set a backup system running, never check the output, and are disappointed years later to learn the initial config was wrong.
Long story short 50% failure of tapes is ludicrous but 50% failure of recovery efforts is not.
Most of these failures are due to:
cartridges being dropped or otherwise physically deformed such that they do not fit into the drives anymore.
cartridges getting stuck in drives and destructive extraction being required.
Data was never written correctly in the first place.
The only exception to this rule that we have seen is tapes written with LTFS. These tapes have a 20 fold higher incidence of failure, we believe because reading data back, as if it was a HDD, causes excessive wear.
Anyone claiming 50% failure rates on tapes has no idea what they are talking about, are reading back tapes from the 1970s/80s or have a vested interest in getting people away from tape storage.