I'm experiencing the problem using Windows 10 on a desktop computer (installed from Windows app store). Assuming the windows install is on C: drive (I did nothing to change default paths) there is 15.3 GB free. We have 4 worlds saved for a total of less than 100 MB.
For me it seems like the problem is that a single world is too big (the biggest world is the one where the error occurs, about 50 MB). I was able to create new worlds (small) and play other smaller worlds (without deleting the large world).