PL/I FIXED BIN vs COBOL COMP sync headaches

Passing a FIXED BIN(31) from PL/I into a COBOL PIC S9(9) COMP field. Values look shifted on the COBOL side for some calls and fine for others.

Is this usually alignment of the containing structure, or should I be suspicious of halfword vs fullword elsewhere in the block?

Map both sides. FIXED BIN(31) and S9(9) COMP are usually fine as elementary items. When it is intermittent, I bet on structure padding before the field, not the integer type itself.

Padding. Again. We added an explicit filler to force the same offset. Lesson refuses to stick.