A timeout is caused when resources are unavailable, causing excessive waits. So, something is going south there. You've narrowed it down to the EMC backup solution running. What do the wait statistics look like during this process? Further, you could use extended events to find out exactly what waits the backup command itself is experiencing. This will help to pretty rapidly narrow down what resource is running in short supply. Probably, it's I/O, disk most likely, but possibly memory, or both. However, go gather the knowledge. That'll tell you where to focus your efforts.