I would start by doing a visual inspection of the drop targets connecting wires for a bad connection. Other than blade switches this machine may use opto’s for it’s drop targets that might be dirty or bad causing the problem.
The self test switch function may help in determining what target or targets have the problem.
All the switches and optos are connected in what is called the switch matrix. This matrix consists of switch rows and columns which connects to the cpu or logic board. If multiple switches are found to be a problem on one row or column, the logic chip that watches those lines may be the problem. If only one switch is problematic chances are it’s a connection problem.
You can interact with the ChatGPT Bot in any Chat Room and there is a dedicated room. The command is /ai followed by a space and then your ? or inquiry.
ie: /ai What is a EM Pinball Machine?