When you mention difficulty booting: how many flashes do you see the MPU make? The initial quick flicker from the LED should be followed by seven solid flashes on a proper boot.

First suspect in this kind of lockup is the chip sockets.

Here is the schematic for the board.
https://www.ipdb.org/files/4497/Bally_1977_Night_Rider_Schematic_Diagram_paginated.pdf

Sockets are extremely difficult to troubleshoot if it is them that fail in this way - just the act of probing the chips could make good enough contact for it to work.

If they are the original style single wipe sockets (closed frame, little rectangle on each pin, if you pull that frame off there's only one contact) just replace them.

It could also be the rom chips themselves.

It's worth trying to fix. If you do have to replace it just buy one of the ones that people take out and replace with new - lots of people (especially resellers) just replace the boards so people have peace of mind/they don't have to worry about servicing new boards so there's lots of perfectly working boards available, usually not more than $100 or so.

Don't forget about power. So very often the orange 12v unreg return wire between the SDB and rectifier board burns up and the 5v/12v will drop out or go low. If it is intermittent it will make the power on reset circuit kick the MPU into getting reset and then it comes back on when the 5v/12v becomes good again. This comes up A LOT. (ground mods band aid it).

Gentle flexing on the MPU and put your finger on a chip and kind of rotate it back and forth will usually expose a flaked out IC socket. The -17 MPUs had really bad IC sockets.

The games without a sound board will look like a reset when they slam. They just start the flash sequence over, so that is something to consider.