Users open shared files but they get an error that file is already open when actually its not

Question

we have a windows 2012 r2 environment with a hyper-v cluster with 4 virtual servers (2012r2) that are located on an hp storage.
users in the office work on windows 7 pc's and sometimes (more than once per day) when they try to open word or excel files from a shared folder they get a message that the file is already open so it opens in read only mode and they cannot save it. we are
pretty sure and tested that that folder is not open from any other user, because some users tried to open files randomly back from 2012 and they got the same errors again. 
i cannot reproduce when i want the problem. i may try reopening files for an hour without having problems.
i tried also to write down the hours that the users may have mostly the problem but i couldnt figure a specific time on the day that the problem occurs.its random.
i want to also notice that we have symantec backup exec 2014 and taking backup on tapes and on deduplication folder with the advanced open file option set to "let VSS to select automatically the provider"
the file server does not record any events in system or dfs replication tab. they only events we got once per 1 or 2 days are in the application tab and its exactly this "the volume recovery was not optimized because an error was encountered:
the file move failed 0x89000016) event id 257,defrag"
i hope i gave u an accurate description of my problems. i really have to solve this.
kostask

Answer 1

Hi Kostak, 
Have you tried to use Process Explorer?
More info: https://technet.microsoft.com/en-us/sysinternals/bb896653.aspx
Simple usage: Part 1: Using SysInternals Process Explorer to solve issues
when trying to clean up files and folders...
This is what I am using to track file handles when tried to open or deleted. Normally I am finding that backup/vss process has taken, antivirus was scanning, or indexing services were working. 
I would recommend you to do the next:
- Disable Windows Search from: Control Panel> All Items> Programs and features> Turn Windows Features On or Off> Uncheck Windows Server. Go to services.msc and Stop Windows Search service.
- Exclude affected folder(s) or drive(s) from antivirus scan/protection, at least 24h.
- Disable backup/vss operations on the drive(s) for at least 24h.
Hope it helps, I know how itchy can be this kind of issue at the office :)