I haven' t seen this, but it' s listed here as a VIP SSL error:
Error 22 description:
fts_alert_desc_record_overflow=22 â€“ a TLSCiphertext record
was received that had a length more than 2^14+2048 bytes, or a record
decypted to a TLSCompressed record with more than 2^14+1024 bytes
Perhaps look at your VIP traffic to see if there' s something funny going on there? Sounds like some kind of hacking attempt, perhaps.
Fortigate 600C 5.0.12, 111C 5.0.2