Phone Number Data Field in Online App Cursor Skips Ahead

Online app that I use for invoicing and tracking customers has an issue when entering a phone number in the data field. The cursor jumps ahead as the number is being entered. I have to back space in order to get the cursor back to where it needs to be to correctly enter the number. This only happens on the Firefox browser. I have Uninstaller and re- installed. The issue persists. The issue does not occur with Firefox on duckduckgo browser. I am attaching a video link for clarity because the file attachment below does not show videos in the list.