Mac mail app shows wrong message body
When I have a set of messages that consist of a conversation with replies back and forth, selecting a message to view only works for the first selection. If I then select another message in the conversation, I see the message body from the first selection. This continues until I select a message outside the conversation and then go back to a message that is part of the conversation. (I'm using the term "conversation" rather than "thread" since I do not display messages in threads. Note that this problem only exists on my Mac. On my iPad or iPhone, the messages display properly.
(I tried a popular solution from Linc Davis dated Aug 20, 2014, but it did not solve the problem.)
iMac 21.5″, macOS 10.13