I had the same problem recently and went through the same frustration that you are going through. I checked the Forums and found many suggestions including switching browsers, etc. I came across a very easy suggestion and tried it. It worked for me and hopefully it will for you. I too use the sort "From" to clean out my In Box & Trash. When you press "Sort By" and get the list of sorts, look at the last choice - it should be "Conversations" - If that is checked (mine was) uncheck it and try the "From" sort again. As I said, it worked for me and have not had the problem again.
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