I know this is late, but I recently began experiencing the same problem with my Child of the Ocean sims. They do not always have issues with kuala pork but it does happen periodically. Sometimes, for whatever reason, they apparently think its fish, not pork, and get the sad buff as a result. This has happened both with neighbor-supplied kuala pork as well as some cooked at home in the pit. It only seems to happen with the kuala pork and, as noted, not all the time, although it seems to happen more often than not. It's really kind of weird. I should also add that it definitely seems tied to the Child of the Ocean trait, not being a mermaid.
