Just reassembled an 8088 lunchbox PC after a failed attempt to get a Gotek installed (will make a later post about it) and the LCD was dead. Opened it back up, disconnected and reconnected the connectors and tried again. Now it works fine. Closed it all up and it's dead again. Tap it and it goes out. Tap it again and it comes back. The DIP / ribbon connector goes together with very little resistance so I suspect it is not making a good positive contact. Just to make sure it wasn't a broken cold solder joint on the connector I resoldered the connector but the problem persists.

The first thing that comes to mind is dielectric grease that you get for automotive use like trailer brake/light connectors. But I imagine there's something better for small electronics like this.

What is the best remedy?