Full and differential backups are taking way longer only from one server I see a perplexing issue on one quasi-production machine (SQL Server 2008 SP2 standard edition) only. Full and differential backup job all of a sudden started taking 48 hours since 2/4/2017. Full backup usually finishes within an hour and differential within minutes. There are four other servers backing up to same share and backup succeeded as usual. They are all virtual machines running on VMWARE and share same underlying SAN. 

Sysadmin doesn't see any issues with SAN as well as backup share. I don't see any blocking. Replication from that machine is running fine. Transaction log backup job is running fine as most databases have simple recovery model. I can ping to backup share from machine which doesn't timeout. 

I use Ola's maintenance solution. Cleanup jobs ran successfully as well. msdb database size is under half GB. Please let me know if I am missing an elephant in the room. 

Here are waits on server. Full backup and differential backup jobs (different databases) are still in progress. I took full backup of a small database (60MB) locally and it finished in no time. Thank you.
Resolved. There was antivirus software trying to scan backup file as it was being created. Once sysadmin fixed it, differential backup finished within minutes as opposed to taking 2-3 hours.