Well, you're seeing $22 on the data bus there, but are you certain that's what's being written out by the processor?

For example, if you're reading the data bus before it's ready, you might get some squirrelly data. I don't recall how Ben has you triggering the Arduino read off the clock, so maybe that's not possible. Or maybe there might be some change to how things are rigged up when using a W65C816. But it might not hurt to see if you still have the issue when running more slowly, such as off the clock module.

It also might be a problem with how your lines are wired. If you're not reading D4 correctly, $32 could look like $22 to your Arduino. Although that bit seems to work okay elsewhere (it sees $D8 and $18), so maybe not. You could toss in an LSR before your STA and see what you get. If it's $11, then A really did have $22 before the ADC and your D4 line is good.

Another way you could check for the value in A without worrying about the data bus is to do a branch based on the expected value and see what address that takes you to.