Just in case anyone has this problem too:
- the bug went away after a few days (a little over a week), now the save function works perfectly again
- meanwhile or if this persists, an alternative option I used as a workaround is to create your survey in the designer and save the JSON file of the survey (download button on the top right when you are on your survey page). Then import the JSON file as a new survey (in Pavlovia: Dashboard > Surveys > Import Surveys > Browse or Drag-and-Drop your JSON file).