An employee experiences a strange effect when creating a new ticket in JIRA:

After typing 3 letters in the input box, the cursor jumps to the left, and it keeps doing that after every few letters.
I had her clear the cache/cookies/etc, restart the browser etc. The problem does not occur in Google Chrome, with the same machine and account.
Does anyone know what this is and how to fix it? (Edge is company preferred browser.)
Thanks for any advice and tips.