TL2000 - getting persistent problems on our weekly full backup

We've got an ageing TL2000 (six years old) that seems to be throwing up problems mainly at our weekly full backup (our Mon-Thur differential backups are not throwing up errors, just the inevitable warning that the full backup was not complete).  Media problems (bad tapes) will disappear after we re-inventory. We're using ArcServe 16.5 SP1. The weekly backup when complete uses three LTO6 tapes for two sessions (C: and D:).
Last week's job gives a good summary of what's been happening in January:

E3392 19/01/2020 16:37:30 2450 1 Backup server TCP reconnection timeout. (AGENT=xxx, Network Error=10054)
W3550 19/01/2020 14:11:40 2446 Failed to connect to media.(MEDIA=W-VMS-FRI- 1/17/20 [S/N: 000034L6],SEQ=1,EC=EARLY WARNING)
E6918 19/01/2020 13:58:49 2446 The tape drive needs cleaning: 1. If the operation has stopped eject the tape ...
W6971 19/01/2020 13:58:49 2446 ***DLTSage Alert*** The following info is for Device[1], S/N[10WT004387]
E8005 19/01/2020 13:58:48 2446 Marking Slot[1] Off-Line after media failure. Slot[1][SN:000046L6] in Library[2][SN:yyy]
E3712 19/01/2020 13:55:44 2447 Unable to close session. (EC=UNRECOVERABLE DATA ERROR)
E3719 19/01/2020 13:55:43 2447 2 Unable to write to media. (MEDIA=W-VMS-FRI- 1/17/20 [S/N: 000046L6], EC=UNRECOVERABLE DATA ERROR)

The cleaning tape has been loaded 47 times. Library firmware is F.11 / 3.20e

We've had occasional errors like these previously, but they haven't stuck around like this. Is it just old age? New cleaning tape required? We were due to replace the unit this financial year but it's now not due to replaced or superseded until next financial year. Anything we can try in the meantime?

Thanks for any help,
Colin.