Python 3 os.renames Access Denied only when used in a script - python-3.x

Question

So I wrote a deployment script in python that essentially just moves a bunch of directories around. It may or may not be relevant that I'm working on Windows and the scripts manipulates files and directories in Windows network shares.
A requirement of this script is it moves the old binary directory to a backup location on the same Windows network share, and that's where I'm having the problem. I'm using os.renames for this task. The destination path is generated based on the timestamp of the executable in the bin directory.
exec_mtime = datetime.fromtimestamp(os.path.getmtime(server_exec_path))
new_dirname = os.path.basename(target_path) + '_' + exec_mtime.strftime('%Y-%m-%d_%H.%M.%S')
backup_target_dir = os.path.join(server_old_dir_path, new_dirname)
if not os.path.exists(backup_target_dir):
print("{0}: Backing up old software...".format(server))
os.renames(server_target_path, backup_target_dir)
else:
print("{0}: A backup already exists with the same version number. Skipping backup.".format(server))
As for my variables:
target_path == "//server/share/path/to/bin"
server_exec_path == os.path.join(target_path, 'Program.exe')
server_old_dir_path == "//server/share/path/to/bin_backup"
The os.renames command would resolve to something like this:
os.renames("//server/share/path/to/bin", "//server/share/path/to/bin_backup\\bin_2019-11-01_13.02.27")
So, my problem is that os.renames always throws PermissionError: [WinError 5] Access is Denied. I have double-checked the permissions on all of these directories and I have them. Here are some things I have tried so far:
Performing the same moves in the Windows file browser. -> It works.
Running the same os.renames command in the python3 shell with the same arguments the script would give it. -> It works, confusingly.
Putting the os.renames command in a loop to retry it 100 times if it fails (I read somewhere that it can help sometimes). -> It fails.
Running the script in an elevated PowerShell. -> It fails.
Hitting my laptop with a sledgehammer. -> Haven't tried yet.
Another thing I want to mention is the script used to work not even a few days ago. I did make some edits in the meantime, but they weren't related to this section of code.
I'm out of ideas on this one. So any help you can provide would be much appreciated.

Answer 1

As it turns out, the problem was a side-effect of the changes I made to my script. I use python to launch a psexec command against the same remote machine earlier in the script (to run taskkill locally so the software I'm updating can exit gracefully), and I used the -u flag, which changes the user with which the command runs on the remote machine. When I removed the -u flag os.renames started working again. So I'm guessing that somehow running psexec changed the user the python script uses when running os.renames.