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