I tried really hard to phrase that as a question and failed. Anyway.
This is an occurrence I have observed multiple times recently. It happens like this:
Two people will be editing a question/answer at the same time. That is to say, they are both working off the same source material for their edit.
One of them will change paragraph A of the post and submit their edit.
The slower editor will change paragraph B of the post, having not noticed the error in paragraph A, and will submit their edit.
The result is that paragraph B is correctly edited, but paragraph A is reverted to its original unedited state, as it appears in the second person's edit.
I'm proposing that if two edits are going on simultaneously, and one changes something that the other does not touch, the second edit should not override the first edit in that segment of the post. Or there should be some system in place to notify the second editor of what has just happened and allow them to adjust accordingly.