A few weeks ago I had a problem with the § and < keys being "mixed up in software", (but physically the keys are in the right locations). I thought the 10.15.2 update resolved it, but now alt+2 produces ™ but it should produce @. It used to work fine, problem started some weeks ago. Sometimes I use an external PC windows keyboard. Macbook pro mid 2014 retina, 13 inch.