I had the same issue. The wording around the tape backups leads you to believe you should be able to easily do a synthetic full backup to tape each day, however it does not work consistently due to the factors mentioned above. The way I found to deal with this is to switch your backups to Reverse Incremental so your most recent backup is always a full backup. This will insure that a full backup is written to tape each night. According to Veeam support this is the recommended best practice when running full backups to tape.