I know of two circumstances that trigger such errors:
In the very unlikely case that a tape fills exactly when a file mark is to be written, DP used to be unable to deal with that. It had backtracking logic to deal with tapes filling in normal data write forever, so it can make sure a file mark always fits when EOM is reached during data block write. I don't know if that has been fixed with current versions, I've seen it once with 6.00 or 6.11 (it really is highly unlikely to hit this, so if you see it repeatedly, I doubt that's your problem).
Plain old device issues. SCSI cabling and termination of the olden days, or their modern offspring (FC interactions with other initiators in the zone, iSCSI hickups of all kinds etc. pp.).
You will probably have to consult the media.log to see if there is anything there explaining the issue further, also look up OS logs (System Events on Win, dmesg on Unix). If that is inconclusive, draw a tape drive support ticket (either through library WebUI [dunno if ESL has that feature like MSLs have], or through Library and Tape Tools [L&TT]). View the ticket thoroughly in the L&TT ticket viewer (select "Everything"). Typically, something pops out somewhere that explains the issues. If all else fails, a HP support case is probably called for, but having media.log and the drive ticket ready will greatly speed this up ;)