Key Down issue while mentioning someone

[Msspl-PrashenjeetRoy]

@ivirabyan
When I mention someone with @ and then authocomplete list is open. When I am using arrow key and go to the last item in autocomplete list. The cursor goes to the starting of all text and all the existing mention getting unwrapped.

In the screenshot you can see the cursor goes to first and autocomplete hangs.

Do you have any suggestions for this issue.