Two Media pools are created for Daily and Weekly and some tapes been allocated to it;
oNoticed if the Drive is busy and another job started, (while this job is waiting for the first backup to finish, upon the first backup finished, tapes are not reloaded automatically by Veeam). Insert a Valid Tape into the library, last written tape: 0000L5. Even though, tapes already available and ready to be used in the Weekly and Daily Pools.
And what was the option for media set creation you used before? I assumption is correct it was create media set for every backup session – which means when the first backup to tape runs it closes the current media set which makes existing tape no longer appendable. More details about the media set creation option here
Do not create, always continue using the media set
It means the tape job will continue to use existing tape media until its full. Once there is not free space left – tape job will pick another free tape media.
I have configured the Backup to Disk Tapes to backup the Backup Job and scheduled it to start after finishing the backup job. (This method didn’t start at all).
This one needs to be checked by support's team.
Backup to tape speed I’m getting max 83MB/s min 43MB/s, but always on average of 71MB/s.
Check if hardware compression is enabled in conjunction with Veeam compression. Disabling hardware compression can increase the performance a bit.
Backup To Tape of Veeam Backup Files:
If this job is configured, and selection on the Folder of the Veeam Backup To Disk directly selected, the entire contents backup chain of that folder is copied to Tape, with regards to the Pool Set as destination.
It's more likely the behavior of the File to tape job, isn't it? File to tape job knows nothing about the backups and backup jobs – it simply pulls all the new files inside the selected directory based on the modification date. All files during the full backup run and changed ones during the incremental run.