Unhandled internal error when syncing to Pavlovia

I created an experiment in the Psychopy builder (consisting of some instructions, simple staircase and edited decision-making task from the Psychopy demo). All works as expected on my computer, but I cannot sync/upload the experiment online: Unhandled internal error. I can’t figure out what is the problem. Could anybody help, please?

This is the error I am getting:

Traceback (most recent call last):
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\builder\builder.py”, line 1221, in onPavloviaSync
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\app\builder\builder.py”, line 719, in fileExport
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\scripts\psyexpCompile.py”, line 73, in generateScript
compileScript(infile=exp, version=None, outfile=filename)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\scripts\psyexpCompile.py”, line 242, in compileScript
_makeTarget(thisExp, outfile, targetOutput)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\scripts\psyexpCompile.py”, line 214, in _makeTarget
script = thisExp.writeScript(outfile, target=targetOutput, modular=True)
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\experiment_experiment.py”, line 236, in writeScript
File “C:\Program Files\PsychoPy3\lib\site-packages\psychopy\experiment\loops.py”, line 602, in writeInitCodeJS
AttributeError: ‘StairHandler’ object has no attribute ‘writeInitCodeJS’

I don’t believe that the staircase has been implemented online yet.

Thank you!