Anyone have experience with the GBAPII++ RTG card?

[Vypr]

I've now built two of these cards and only managed to get one working.

Card 1 was the first built card, I had problems with graphical corruption (lines down the screen) even though it passed allt he hardware diagnostics (memory tests passed flawlessly) and if you ignored the lines it worked fine. Eventually I replaced the RAM chips and it is now working perfectly. Strange that even though the RAM passed all the checks it seems like the Cirrus Logic chip just didn't like this specific brand of RAM.

Bolstered byt his and since I had enough bits left over, I built another card and this one is giving me headaches.

Unlike the 1st card, the display works perfectly, but after about 10-15 minutes use the system locks up with a blank screen with a wavy right hand edge. The RAM tests show something funky going on with the memory.
Occasionally it appears to have difficulty writing to the first two bytes.

If I do a memtest on the graphics memory I start off with this (Just testing the first 16 addresses):

NORMAL-2-test from $0020.0000 to $0020.000F, press CTRL+C to abort...

Long ERROR @ adr.: $200000 (expected: $00000000, got: $FFFF0000)
Longwise tested area: $200000-$20000F; pattern: $00000000; errors:1

Long ERROR @ adr.: $200000 (expected: $55555555, got: $00005555)
Longwise tested area: $200000-$20000F; pattern: $55555555; errors:1

Long ERROR @ adr.: $200000 (expected: $AAAAAAAA, got: $5555AAAA)
Longwise tested area: $200000-$20000F; pattern: $AAAAAAAA; errors:1

Long ERROR @ adr.: $200000 (expected: $FFFFFFFF, got: $AAAAFFFF)
Longwise tested area: $200000-$20000F; pattern: $FFFFFFFF; errors:1

Running consecutive tests on the same are, more and more errors creep in, always on the first two bytes.

What I have done so far:

Tested all the Address and data lines for continuity
Tested that the RAS, CAS and WE lines for continuity and the correct resistance to the Cirrus Logic GPU (Showing as 22 ohms which is what it should be)
Checked the clock signal was present and wasn't showing glitches
Swapped the RAM chips
Swapped the Cirrus Logic chip with the one from the working board.
Swapped the CPLD
Swapped the voltage regulator
Checked all the passive components are soldered down properly and are the correct values.

Anyone have any idea what else I can check?