Tangential (slightly) but given the repro case, perhaps relevant:

Why is buffer-undo-list   not set up to avoid saving undo information in
shell buffers?
AKA, should we have (setq buffer-undo-list t) in shell buffers? Perhaps
even in all comint buffers? I dont think I have had reason to "undo" in
a shell buffer, and even if I did, I dont quite know what that means.

-- 

Thanks,

--Raman
♈ Id: kg:/m/0285kf1  🦮