Although I don't know the exact answer for this problem, but I would use a workaround here:
In the "Auto Trader" sheet (cell A3) I would use the FILTER function as follows:
=FILTER(Dealers!A:D;Dealers!E:E="X")
This will produce all the lines from "Dealers" worksheet which matches the criteria that in the appropriate AutoTrader column it has an "X".
Unfortunately, this is a workaround, since you have to do this for all worksheets, modifying the formula accordingly. (like for the next - Cars.com - worksheet: =FILTER(Dealers!A:D;Dealers!F:F="X")
Hope it helped anyway.