How to reproduce: launch minecraft 1.12.2 with FoamFix 0.10.10 and CTM 1.0.1.30.
The log will show an error about being unable to override the minecraft:models/item/fishing_rod model.
First line of the error:
[15:43:31] [Client thread/ERROR] [FML]: Could not load override model minecraft:item/fishing_rod_cast for model minecraft:models/item/fishing_rod
The whole thing:
https://pastebin.com/f2iiwyC4

The error does not appear if one of the two mods is disabled, even if many other mods are added.
The error disappears if Foamfix's coremod is turned off in the config via forceDisable, but as long as the coremod is not forced disabled the error will appear even if all options under Load Time Configuration are turned off.
The error also still appears after the client configs deduplicateModels and deduplicateModelBakers are turned off, so I'm out of ideas as to whay might cause the problem.