Ok, I'll post what I did:

- compare file with other feagv9 dump, see 2 bytes differ, 2 bits flipped, immediate suspect that one of the two files is a bad dump
- compare both files to the other 3 revisions, see that new dump matches all 3 other revisions with data from that area
- conclusion: old dump is bad

approx 0.5% uncertainty comes from, maybe there's a 5th revision with 2 bits flipped, and no changes to the other ROM (note: rom data is 16-bit, mapped interleaved)