Today (11/21) was on ua 1553 ord-smf and as we were deplaning
They announce in airport that baggage retrieval will be delayed due to a weight and balance issue on the plane and to stay upstairs and get lunch if we want because it will be a while. 30-50 minute estimated delay

How does this happen? Anyone heard this before? Had to do clever w&b when loading plane so offloading might cause a problem? (I can only envision something really heavy and in back that offloading other bags to get too would cause plane to tip back?

Thought it was weird is all, never heard of weight and balance issues after the flight

Edit: sorry mods maybe this should've gone in pilot q&a thread? Wasn't sure as it is more general