BE 12.5 Ejects tapes

We have BE 12.5 for Windows Servers installed. We previously had 12.0 running but faced problems with jobs failing having unrecognised media. Then we updated to 12.5 with the same problems. Our supplier replaced the drive, HP StorageWorks, with a new one. Currently, BE doesn't give the said error but ejects the tape itself. We tried running a Test Run and it was successful. However, the full backup job itself won't run and would continuously eject the tapes, even new ones. We tried doing a restoration from previous backup tapes but the job also fails.

Any ideas?