Slider not appearing online

URL of experiment: Pavlovia, Sign in · GitLab
What I used: Builder with custom code components
Psychopy version : v2020.2.9
operating system : macOS Big Sur version 11.1 Beta

Description of the problem:
I have a slider component in my routine, where I define in in both custom code and in builder as shown below:

#python version
#begin routine tab
slider.marker.size = (0.05, 0.05)

slider = visual.Slider(win=win, name='slider',
        size=(1, 0.05), pos=(0, -0.35), units='height',
        labels=['LEFT: $20, RIGHT: $0', '$15/$5','$10/$10', '$5/$15', '$0/$20'], 
        ticks=(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20),
        granularity=1, style=['rating', 'triangleMarker'],
        color='Black', font='Arial',
        flip=False, labelHeight = .03)

//JS version
//Begin routine 
slider.size = [1, 0.05];
slider.labels = ['LEFT: $20, RIGHT: $0', '$15/$5','$10/$10', '$5/$15', '$0/$20'];
slider.ticks = (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20);
slider._needVertexUpdate = true;
slider._buildSlider();

This runs locally, but fails online. I get the following error message:

Is there a way to solve this?