It sounds like you have no dc path to supply bias currents, which would
explain the long time constants:

"The op amp non-inverting input is coupled to the output of an LM1972
digital
attenuator via a 1uf electrolytic." Do you mean it's ac coupled?

"The inverting input is tied directly to the output, which feeds a 5532
summing amp via a 0.1uF ceramic cap.  This part is different from the old
circuit in that the now-problematic op amp also fed a 5532 buffer amp with a
Z in of 2.7k via a 10uF electrolytic. "  Do you mean that the output is also
AC coupled?

If so, then neither the inverting or noninverting inputs has a dc bias path.

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