Not having owned a system1 I don't know what chip controls those, however that segment problem is likely due to a bad chip leg on your MPU. Also you said you were new to owning so when you check the displays by removing them don't forget to turn the machine off each time you disconnect a display and re-install it or you will blow those chips. Look at your manual if you have one and locate what chip drives your displays and I think testing will uncover bad legs.

Follow what Force has told you first and if it continues look at those chips as that looks to be a segment problem......which could have initially may have been caused by removing the displays and reconnecting them while the pin was on.