[SeeleyOne]

And here I thought they were pretty obvious

"Attempt to access non-existent containing entity from script
Location: 'eval' script for Component 'Advance' (Eval Script 'Accrue Advances') near line 3

This means that the eval script, 'Accrue Advances', is trying to look at something on line 3. That something does not exist when the eval script is being looked at. Advances probably have a narrow window of timing.

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Attempt to access non-existent containing entity from script
Location: 'eval' script for Component 'Advance' (Eval Script '#6') near line 11

The Eval Script #6 (how many are in that advance?) is trying to look at something on line 11 that does not exist at that time.

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Attempt to access non-existent containing entity from script
Location: 'eval' script for Component 'Advance' (Eval Script '#6') near line 16"

Eval Script #6 is trying to do something that does not exist yet around line 16.

Either a) the timings and phases are out of sync with when an Advance is looked at, b) Advances cannot have eval scripts, or c) both a and b. I am guessing c. This is why I have been recommending that you should use a mechanic to look at the Advance and run the eval script. Then, since you did not seem to like that idea, I recommended an Edge. But really, for this a mechanic is the best. I showed how you can look for an advance in an earlier post.