In the following example, the "Right subplot" should always appear on the right third of the screen and the subplots should never overlap. When I use a spec list like: [[{"colspan": 2}, {}, None]], the left subplot expands as expected to take up the left and center columns, but the "Right subplot" moves into the middle and overlaps the colspanning-subplot. Part of the colspanning subplot is obscured. If I try to force the "Right subplot" to appear in column 3 after I add the colspan, I get an error because column 3 no longer exists. If you uncomment the widths specification, the titles will collide as well. The "right subplot" should remain in the right column even after we introduce the colspan.

import plotly.graph_objects as go
for n in [0,1]:
 if n==0: ##TRIVIAL SPEC_LIST THAT WORKS
 spec_list=[[{}, {}, {}]]
 title_tuple = ("Left Subplot","Middle Subplot", "Right subplot")
 else: ##SPEC_LIST WITH COLSPAN ADJACENT TO A NORMAL CELL THAT FAILS
 spec_list=[[{"colspan": 2}, {}, None]]
 title_tuple = ("Left and Center Subplot","Right Subplot")
 
 fig = make_subplots(
 rows=1, cols=3,
 #column_widths=[2,6,5],
 specs=spec_list,
 subplot_titles=title_tuple)
 
 fig.add_trace(go.Scatter(x=[1, 4], y=[2, 1]),
 row=1, col=1)
 fig.add_trace(go.Scatter(x=[1, 2], y=[1, 2]),
 row=1, col=3-n)
 fig.show()