Anyone experience this problem - and have remedy?

Had multi-worksheet file (let's say sheets A, B, and C). One of the
worksheets (A!A1, A!B1, and A1C1) summarizes the same cells of the others
(A!A1 =B!A1+C!A1, A!B1=B!B1+C!A1B1, and A!C1 =B!C1+C!C1).

Added worksheets (D and E). Updated A!A1=B!A1+C!A1+D!A1+E!A1.

Attempting to drag and drop A!A1 into A!B1 and A!C1. Result is A!B1 and
A!C1 exactly match A!A1. No '$' are used in formulas.

What's up?