Variable Value Changes Based on Return Expression Bug

That's super helpful. It looks like it's changing "Num"  when it's combined with "Denom".

"RETURN Num" evaluates to X

"RETURN Num + Denom * 0" evaluates to a value different from X

I'm still clueless as to why, but now I kind of know what's going on at least.

Can variables be passed between measures? There are some variable names defined in this measure (Y/Y Price Inflation) that are also used in the dependent measure (Cumulative Price Inflation). However, changing the names doesn't fix the problem either..

I've also tried running the "Num" inside a CALCULATE(ALL('Calendar'),...)  clause, but that doesn't fix it.

	CALCULATE([Cumulative Price Inflation],FILTER(ALL('Calendar'),'Calendar'[Date]<TODAY()))
	- CALCULATE([Cumulative Price Inflation],FILTER(ALL('Calendar'),'Calendar'[Date]<TODAY()- 365)) * 0
	=
	CALCULATE([Cumulative Price Inflation],FILTER(ALL('Calendar'),'Calendar'[Date]<TODAY())

 The above returns "TRUE". However when the two clauses are run independently, they do not equal each other.