"Unknown Member used in query" error in Data Load Rule

Summary:

I am updating the Source Filter in an EPBCS data load rule, changing the spec for Accounts, but even using the member selector to ensure correct spelling, I am getting an "Unknown Member used in query" error message.

Content (please ensure you mask any confidential information):

For Account, we have this:

@ILvl0Descendants("AC_400000"),@ILvl0Descendants("AC_900000")

(I changed it from "OFS_Income Statement" to "AC_400000" because OFS_Income Statement was pulling in shared versions of accounts and double-counting).

Here's the line of the generated script, indicated by the log:

CROSSJOIN({Descendants([Account].[AC_400000],[Account].Levels(0)),Descendants([Account].[AC_900000],[Account].Levels(0))