I am having the same problem.
It seems to be on just a few files in my OneDrive where this behaviour occurs.
It appears to have only started after the recent Office updates.
Other files being saved to OneDrive are working fine.
The message that comes up under the _vti_rpc. account is as follows:
https://d.docs.live.net >> _vti_bin >> shtml.exe >> _vti_rpc
It suggest some sort of system call being piped incorrectly.
Whilst I can't be 100% sure, I think the file I am having issues with was open in EXCEL at the time when the Office update was running.
Suspect it is to do with the AutoSave feature, which I notice it writing directly out to the internet. Previously, updates would have been to the local drive and then OneDrive would sync.
I will have a look at the suggestion by Stefan, but since that issue was reporting prior to this recent update I suspect it will not be related.