Sync a local folder with a server via REST API calls?

I currently have the following problem and can't decide which way to go:

I have a local directory with subfolders and files and want to mirror and sync that with a remote directory on a server. The problem is that I don't have any direct access to the server itself. The only access point I have is a bunch of REST API calls such as: uploading a file, downloading a file, getting metadata of a file (including creation and change date) and getting a file/directory list

I have already spent some time to look for possible programs/implementations but none of those have really convinced me. Here are some of the possiblities I considered so far:

1. Use a Powershell or Python script and manually check each file and folder for changes. Schedule a task to call the script every x minutes/hours
2. Use the Microsoft Sync Framework (MSF) and implement a custom SyncProvider which handles the REST calls and translates it into MSF format. Here I can't really tell if it's feasable at all and how complex it would be
3. Use tools like Syncthing or similar, but I couldn't find something that supports a remote sync directory only accessible via REST calls, but as there are quite a lot of tool I might have missed some that do

I'm working under Windows 10 so the solution should run on Windows and preferably not require too many addition resources.

Furthermore the solution should be somewhat resilient to errors as the REST API calls seem to have a tendency to fail sometimes (roughly 1 in 10 calls fails)

Any ideas and suggestions are welcome :)