MFPLI01221S When array cross-sections are used within expressions or an assignment, all cross-sections must have exactly the same bound for each dimension. An upper bound differs in this expression.

Not only must the difference between the lower and upper bounds of each dimension of both operands in an array expression or assignment be the same, but the upper bounds of each dimension must also be the same.
Resolution:
Ensure the upper bounds of each dimension of both operands are the same.
Module:
COMPAT.PL1, VALASS.PL1