Unable to open some vehicle sheets

[McCookies]

I'm unable to open the Actor sheets for the PCs ships. They are slightly customized versions of the Citadel cruiser and Modified Z-95 headhunter. Other vehicle sheets (all unmodified) open fine.

Console shows the following when I try to open any of the 3 sheets:

Error: An error occurred while rendering SWSEActorSheet

25. source?.get is not a function at Hooks.onError (foundry.js:654:24) at foundry.js:5795:13 Caused by: TypeError: source?.get is not a function at getDocumentByUuid (util.mjs:1392:42) at getActor (attack.mjs:975:16) at get provider (attack.mjs:183:16) at lookupProperty (handlebars.min.js:27:24258) at eval (eval at createFunctionContext (handlebars.min.js:29:10011), :11:190) at Object.h [as inverse] (handlebars.min.js:27:25975) at Object. (handlebars.min.js:27:18195) at Object. (handlebars.min.js:27:18372) at Object.c (handlebars.min.js:27:27865) at eval (eval at createFunctionContext (handlebars.min.js:29:10011), :10:54)

[McCookies]

Tested some more. I added a YT-1300 transport from the compendium to my actors. I was able to open the Actor sheet with no problem. I tried to make some changes to it (crew quality, add some systems). That went fine until I tried dragging a weapon system over to the pilot or gunner slot. It didn't stay and the Actor sheet is not openable after that.