i try different settings but nothing works

my setup:
full backup ~2TB data (1 server with 5 vms)
2 rdx drives with 5tb space
5 rdx drives with 1tb space
suggestion for the backup:
full backup once time in a week, to the internal hdd and rdx drives (5tb)
incremental backup daily to the internal hdd and rdx drives (1tb)
what is working:
backup to the internal hdd without any errors works create this is the daily backup job, incremental backup works as well, yesterday only 40gb was copied.
Backup to the rdx drives, is not as incremental backup working. Backup to the 5tb rdx drives is working, but if i insert the small rdx drives veeam try to backup the full backup => out of space
what i try:
first time i create the primary job to backup trough rdx tape,
and the backup copy job was the backup to the internal hdd
my second try was to swap the jobs, but the result was the same.
thanks for your help!