App timeouts during SQL backups

Has anyone any idea why we might experience connection timeouts to a SQL 2016 box when a SQL log backup is running. The SQL box has plenty of resources and uses an EMC backup product. Its an application that uses filestream pretty heavily. The IO susbsystem response times are OK. Memory, network & CPU arent stressed.

Any ideas on how to start looking at this?

Backup should not cause connectivity issues.
What are the database auto growth settings?I guess application is having issue during the auto growth operation.
Are you facing this issues regularly?