Thanks, there’s definitely an issue of the layout, but I can’t even figure out the fare basis code for the return leg to look up the “correct” fare rules on ExpertFlyer. (Which is better than TAP who doesn’t even disclose the booking class…) Interesting that they would refund a portion of the fare - for the US carriers it’s always been that the most restrictive rule applies to the entire itinerary.

I didn’t have time to call BA to inquire before the 24h clock ran out so I canceled and will maybe try again.

But if your offer still stands, not my exact dates/flights, but the same fare:
16-Aug JFK-LHR-LIS BA#182/502
27-Aug OPO-LHR-JFK BA#517/115.