I'm in the same boat as you and I've tried just about everything at this point. I have:

Replaced the 3-pin connector that plugs into the top right of the GI board
Replaced the male header pins for the 3-pin connector on the GI board
Replaced all four 2-pin connectors that plug into the GI board (not the header pins though)
Replaced both connectors in the backbox that connect the bridge rectifier to the GI board
Replaced the bridge rectifier
Unplugged all lighting mods
Turned the GI brightness down

The only thing I haven't done is replace the data cable. I'm going to email Stern to see if I can get a replacement, unless someone knows where to find this data cable? Short of that, I may have to replace the GI board to see if that's the issue.

Any other ideas out there?

Thanks for the reply.

It's a Cat5e cable with what looks to be an RJ12(?) plug. As @Sammi31 mentioned above, the plugs are different (smaller) than on regular ethernet cables. Seems it would be be easy to reproduce with a couple parts and a crimper from Amazon. I'll order the stuff today and let you guys know if this solves it!

MetDataCable (resized).jpg

MetDataCable1 (resized).jpg

MetDataCable2 (resized).jpg

After pulling out what's left of my hair, I have finally solved my strobing issue! I realized that my AC/DC BIBLE uses the same GI board as Metallica. The only difference is that AC/DC had a Rev. D version and Metallica had a Rev. C version. The board from AC/DC has fixed the problem! I've ordered a new one from Pinballlife and will have both games up and running soon.

In my case, it looks like this was not a data cable issue at all, but more likely a bad cable connector on the board or a bad capacitor like Zitt mentioned above.

Thanks for the help guys!

@Sammi31 I see you have an AC/DC in your collection, so you can try the same thing to help narrow down the issue. Let us know!