Error "Failed to decode encryption key" randomly occurs during the backup execution via the maintenance plan (MP).
After upgrade to 8.9.0.511 some MP Jobs with Encryption on fail randomly getting the error "Failed to decode encryption key"
Script example:
execute master.dbo.xp_slssqlmaint N'-D "ALL DATABASES" -BkUpMedia DISK -BkUpDB "D:\backups%SERVER%%D%SERVER%%D%T_%z.bak" -BkFileName -NOINIT -Logging 0 -Reliability 3 -CryptLevel 8 -jobp "Rt1u9iKhTgGGH3xBU3xhUqfxTORjC/r8L/5+lxOcnyKgu5AUXP5BG