I'd like to see a photo of the plugs that were in the outlet. I think they probably need to be replaced too.
Breakers will tolerate a small overcurrent for a long time which makes poor contacts so dangerous. Those old outlets are probably all corroded inside, this leads to a warm connection which accelerates the corrosion, which makes more resistance, which heats the connection more, etc.
Don't tin the wire when connecting the new outlets-follow Mainesail's excellent advice (posted elsewhere on the forum) on terminations.