nitro AN515-57 Black line only on 144hz is there a fix to this?

Those stripes can be caused by either an eDP cable pins at its plugs issue, or the actual either screens 40 pin plugs at the mobo plug or the screen plug ends, which is either with one of its data or power cable or pins not making full contact or its damaged or the last thing that it could be is the actual screen is damaged.

Note: If the laptop is under warranty don’t open it or do anything and get into contact with Acer so that they can repair this problem.

If your laptop is out of warranty then you either take your laptop to a technician (which is the best idea) so that he/she can analyse this problem or you can open the laptop and check the mobo scree eDP cable plug yourself, if its connected fully at the mobo end and the same at the screen end which is allot more involved as you need to take the bezel off and unglue the LED screen panel from the top case/lid, which is a very involved as there is a special method to remove the double sided tape that the screen is glued to the laptop lid.