On Windows 2016, make sure defender is disabled or the exclusions for BE are set on it.
https://www.veritas.com/support/en_US/article.100046324
Take a look at this as well -
https://www.veritas.com/support/en_US/article.100044860
Else if above does not help then repro the loading media behaviour with SGMON.exe ( bengine, beserver, pvlsvr (settings --> pvlsvr or device and media --> select verbose ) . Run the backup with these settings and when the status shows loading media wait for 1 hours. Cancel the job , submit the SGMON Log ( BE Install Path\Logs) --> open a tech support case.