Specifically, the issue is that [our] is a text substitution defined in English Language by Graham Nelson:
To say our:
now the prior named object is the player;
if the story viewpoint is first person singular:
say "my";
if the story viewpoint is second person singular:
say "your";
if the story viewpoint is third person singular:
if the player is male:
say "his";
otherwise:
say "her";
if the story viewpoint is first person plural:
say "our";
if the story viewpoint is second person plural:
say "your";
if the story viewpoint is third person plural:
say "their".
And [their] delegates to it when referring to the player:
To say their:
let the item be the prior named object;
if the prior naming context is plural:
say "their";
otherwise if the item is the player:
say "[our]";
otherwise if the item is a male person and item is not neuter:
say "his";
otherwise if the item is a female person and item is not neuter:
say "her";
otherwise:
say "its";
Counterfeit Monkey is overriding this text substitution (because phrases in extensions can be overridden by defining the same phrase in your source code: this is an intentional feature) and thus [their] is delegating to the new [our] instead of the original [our].
The easiest solution is to rename one or the other. I doubt Counterfeit Monkey uses the English Language [our] anywhere (or this bug would have shown up sooner), so you can use that overriding behavior to make [their] instead delegate to [our-us] instead (and define [our-us] to be the code from the English Language [our]).