Large collection not uploading - operation not permitted

[philpsdf]

I'm trying to do the initial upload of a rather large (200± GB of photos and videos) and onedrived seems to freeze. I suspect it's related to Microsoft's API, but I'm not very experienced neither with it nor with Python.
Running the daemon in debug mode, this is what I get after a while:
[2018-10-09 15:19:26,377] DEBUG: Worker-1: Starting new HTTPS connection (1): api.onedrive.com:443
[2018-10-09 15:19:27,507] ERROR: Worker-1: Encountered connection error: [Errno 1] Operation not permitted. Retry in 60 sec.
[2018-10-09 15:20:27,605] DEBUG: Worker-1: Starting new HTTPS connection (1): api.onedrive.com:443
[2018-10-09 15:20:28,418] ERROR: Worker-1: Encountered connection error: [Errno 1] Operation not permitted. Retry in 60 sec.

And it goes on and on. Has anybody faced this issue as well?