I'm trying to create an interactive stacked bar chart that displays the data for a given slider value. The entire data is stored in a base dataset and the data displayed is a subset of this base dataset. The problem I'm facing is that the code basically works, but only the first time a change is issued.

Here is a minimal example:

from bokeh.layouts import column
from bokeh.models import CustomJS, Slider
from bokeh.plotting import ColumnDataSource, figure, output_file, show

import pandas as pd

base = pd.DataFrame({'a': [1, 2, 3, 4, 5, 6],
                     'b': [10, 20, 30, 40, 50, 60],
                     'c': ['x', 'y', 'x', 'y', 'x', 'y']})
edit = pd.DataFrame({'a': [1, 2],
                     'b': [10, 20],
                     'c': ['x', 'y']})

sbase = ColumnDataSource(data=base)
sedit = ColumnDataSource(data=edit)

p = figure(x_range=['x', 'y'], width=200, height=200)
p.vbar_stack(stackers=['a', 'b'], x='c', width=0.9, color=['#7570b3', '#1b9e77'], source=sedit)

slider = Slider(start=1, end=3, value=1, step=1, title='slider')
slider_callback = CustomJS(args=dict(sbase=sbase, sedit=sedit), code="""
    const sid = cb_obj.value;
    const bs = sbase.data;
    const ed = sedit.data;
    
    var ix = sid*2-2;
    var iy = sid*2-1;    
    
    ed['a'] = [bs['a'][ix], bs['b'][ix]];
    ed['b'] = [bs['a'][iy], bs['b'][iy]];
    
    console.log(ed)
    console.log(sedit.data)
    sedit.change.emit();
    console.log(sedit.data)
""")
slider.js_on_change('value', slider_callback)

output_file('test.html')
show(column(p, slider))

I'm kind of at a loss, because, according to the logs, the underlying data does change with subsequent inputs, but the chart still remains frozen.