It was caused by careless placing of the new siege leader trait in 00_traits.txt
Make a copy of your entire game folder for playing 1.103 games.
In this copy locate the folder /common/traits
Inside it are 3 files 00_traits, 01_traits, and 02_traits
You will find and entry in 00_traits.txt like this:
siege_leader = {
leader = yes
command_modifier = {
.
.
.
}
}
Copy that entire entry.
Open 02_traits.txt
At the end of that file, on a new line, paste that entry.
Delete the original entry from 00_traits.txt
You can use this copy of CKII for your old 1.103 games.
DO NOT START NEW GAMES ON THIS COPY
THEY WILL NOT BE COMPATIBLE WITH FUTURE PATCHES.
This fixed my modded game. Thanks a ton!