Ours is Multi server (2 WFE and 2 APP) SP 2016 Env.
However if we try to select only WSPs or other smaller component It moves to Step 2. Not able to make out what is going wrong today. We have been backing up the farm through C.A. for past many months.
When trying to Backup using PowerShell
Backup-SPFarm -Directory "\\servername\test backup" -BackupMethod Full -Verbose
There is Free Disk Space is 50 GB, whereas the backup always ranges between 28 GB.