Thanks for the response!
I was on v2.1.4, and have just updated to 2.1.6. The crash has been reported again by another player after updating (at yet a different event), so the version didn't seem to be the issue.
The choice template does have pictures. There are 2 choices, and the parameters set 2 choices with pictures:
While the template was only set once, both the choice run after it and the nested choice had the same number of choices (2), so it shouldn't have had the wrong number of choices.
To confirm that the nesting wasn't the issue, another player reported this crash today:
For this one, the event looks like this:
This event has no nested choice, and has 3 choices. Its template is set up the same way, and has 3 choices set (each with a picture).
I should note that none of the choices have picture settings in the "Pictures Settings", just a picture selected in the choice settings (the text for the choice is set to a blank character " " so you just see the pictures in the dimmed choice menu instead of text, like this:
My pictures settings look like this (default):
I will try replacing that function in the plugin code as you suggested and see if that does anything to help.
Thanks!