CONTINUE...
All of the ROM dumps check out – all is as it should be.
One issue you may encounter when working with ROMs – sometimes the type of ROM is not written on the chip (this is common with mask ROMs).
When that happens, we find the MAME driver file of the game board – this file is like a mechanic's manual. For many games, the MAME driver lists which type of ROM is used, which type of RAM is used, the type of processors, etc and their location on the board.
Schematics (the topology of the electronic circuits) are also very helpful when available, but unfortunately this board has no schematics.
The MAME Driver for Raiden 2 is:
https://github.com/pongnguy/mame0148s/blob/master/src/mame/drivers/raiden2.c

When there are no problems with the ROMs, the next procedure is a bit delicate.
One of the most common problems with these boards is lifted legs on the custom chips.
With my X-Acto knife, I tested each leg one by one to see if any are disconnected.

All of the legs are solid.
After eliminating the ROMs and custom chip connections, it's time to look at the RAM.
After a little bit of tinkering with my logic probe, I couldn't get pulses on some legs of the two 6116 RAM chips highlighted in red. Since there was no further information (like schematics) with this board, I decided to "take a shot in the dark" and replace those 2 RAM chips.

I know these RAM chips are responsible for palette data – maybe replacing them will solve some problems.
Here, I'm installing sockets and replacement parts for these two friends:

We have a little accident every now and then. I must have overheated the board a bit during disassembly with a hot air gun because a small part of one of the traces lifted up. I thought it was the residue of the cotton swab I used after soldering (to clean the flux) and when I pulled the swab away, the trace itself came up.
Anyway, I immediately patched it and continued on my way.

One of the 6116 RAM chips I removed failed testing:

I immediately checked the pinout:

I see that I have the same MB8416 chips that I bought previously for an Asterix repair.

I changed the RAM and tested the game, but nothing changed.
Then I tested the old RAM again:

Turns out the old RAM is good after all.