My part dimension isn't updating to the global variable that I set it to.

I have variables set up to be defined in a text file, and when I update them there and rebuild they update in my part's equations editor (both the global variable value and the equation which sets the sketch dimension update), but the part doesn't automatically update.

Photo below shows what it looks like when I changed the 'BoxHeight' variable to 10 (from 20) in the text file, rebuild the part, and open the equations editor. As you can see, box height has updated to a value of 10, the equation "D1@Sketch1" = "BoxHeight" now evaluates to 10, but on the part, the dimension (the one of the left of the part) still has a value of 20 (that's D1@Sketch1).

When I go in to edit the dimension, I get this: "Global Variable 'BoxHeight' already exists":

And it proceeds to tell me it's set to 'BoxHeight' which evaluates (here) tp 20", even though it's now evaluating to 10" (as it should) in the equation editor.

Pressing rebuild in the dimension does nothing. The only way I've figured out to get it to update is to click on the equation value in the editor and, without changing anything, press OK. Then the part updates.

(like this, except with a green check mark in the blue active field, I cannot click away before clicking ok, then it doesn't work)

Other parts that I created in the same way (but which are simpler) appear to be updating just fine. So I don't think it's an issue with my solidworks or windows, but likely something broken within the part.

Please advise.