1st) try the old screen (if it still works) and see if the touch function is normal.
2nd) If it works normally, install the new iFixit screen and see if the touch is still finicky. If it still has issues, you should order a new screen.
3) If after your repair neither screen works (the old one or the replacement), then there may be something stuck in the connector (ie. adhesive, dust) or possibly a damaged prong, or worse, a damaged board. In that case, a new screen isn’t going to help you.
Best of luck! Let us know what the result is!