Git force push fails after a rejected push (unpack failed)?

[X H <music_is_live_lg@hotmail.com>]

Hi,

I have a remote repository on a network share configured as a file remote.
I have pushed the HEAD of a branch to the remote, then amend the local HEAD. I then try to push the HEAD again but it was rejected.
I made multiple attempts and then try to force the push with: $ git push -f origin branch_name but it failed with message:

remote: error: unable to write sha1 filename objects/d9/4bfb39cd0be7497e493bd4045111a7b1158134: Permission denied
remote: fatal: failed to write object
error: unpack failed: unpack-objects abnormal exit
To file://xxx
 ! [remote rejected] branch_name -> branch_name (unpacker error)
error: failed to push some refs to 'file://xxx'

Sometimes the error is due to a commit sha, sometimes due to a tree sha.
It seems that after a rejected push some files are not deleted and since they are read only on the remote, the next push cannot overwrite them.

Is it the intended behaviour? I try to reproduce this and it seems it doesn't happen always.

git v2.3.5 (git-for-windows)

Thank you.