Mhm, you posted a log from Version 1.3.4 which is pretty old.
You wrote this happens also with 1.4.5
Can you provide a log of this version please?
From the log I see that you are using WebDAV as interface.
Questions:
Does this happen only with office documents?
If yes, do you have the Office Upload Center active?
If yes, please read this post and why Office Upload Center interferes with WebDAV connected vaults