I have the same problem on my Galaxy S7 Edge and it also occurred on my Galaxy S5.
The files ALL begin with the following text :
SERVICE com.samsung.vvm/.service.VmailDebugService 43a40140 pid=29586
Client:
VmailDebugService
This appears to be text generated by or supporting some kind of system level testing/debugging utility. I now have over a thousand of these things and the files I care to deal with are interspersed with them which kind of makes it cumbersome, at times, to actually find MY files.
I'm manually deleting mine to make the library of files useable...no problems.
Would like to see these not appear in the first place.