Unable to Sync local with online

URL of experiment: https://gitlab.pavlovia.org/csea/fall2020_3031b2

Description of the problem:
It looks like the study is unable to sync with Pavlovia after collecting (and subsequently saving) data externally that isn’t in my local root folder. I made changes to my local experiment copy that I would like to sync up into the server, but I got an error trying to sync. So I tried downloading the whole external copy of the study from Gitlab, which has the subject data, copying that to my local root folder, and then trying to sync (under the assumption that the only difference would be the local study changes and these would get pushed to the Pavlovia server perfectly as before). But then I got a slightly different error (“updates were rejected because the tip of your current branch is behind its remote counterpart. integrate the remote changes e.g. git pull”)

Original Error:
(hint: Updates were rejected because the remote contains work that you do
hint: not have locally. This is usually caused by another repository pushing
hint: to the same ref. You may want to first integrate the remote changes
hint: (e.g., ‘git pull …’) before pushing again).

Most recent errors:
After copying things over from Gitlab manually, my most recent error is “ValueError(“Found an unexpected change_type ‘{}’ in gitpython Diff”.format(this.change_type))”
But I also followed the guidances in the other related posts (notably the one below), but was unable to get any results using the “sync” tab in Window>Search Pavlovia (error in runner: “CONFLICT (add/add): automatic merge failed; fix conflicts and then commit result”). I don’t know how to use Gitlab, if the changes need to be made in some specific interface there. Any ideas?

Guiding Source: