LSP Breaks or Breaking undo After Automatic Line Split

I recently switched from many deoplete-based plugins to native lsp. So far, I like the way my new environment is working. But, I just recently noticed that ‘undo’ isn’t working correctly in a particular but common situation.

When I am in a LaTeX document with LTeX LSP sever active, and when I append characters to the end of a line beyond the ‘textwidth’ limit, nvim automatically breaks the line, which is what I want. However, if I then exit insert mode and ‘undo’, the characters I added to the end of the previous line are removed but the characters inserted on the next line are not removed! This is completely wrong, and never happened before in vim or neovim.

I’m certainly willing to troubleshoot more, and I will do more of that, but I haven’t had a chance to binary-search my whole config file. But, I found this:

So, I know I’m not the only one who has noticed issues. Does anyone recognized this spurious behavior?