Ha! Yes I noticed that too and have fixed in the latest release of gphotosdl
Thank you very much for all your testing and I'm glad you got your photos moved.
There are some unknowns around rate limiting.
Copying the entire browser directory should let you run it elsewhere. This needs to be more explicit in the docs.
Also we are missing a -profile flag which would let you run two at once.
Being able to download multiple at once would be a good idea.
Interesting that you are having problems with the gphotos API rate limiting you. You could try --check-first so it does all the API work at the start.