Bit of an update:
Opened the resolver at the bottom of the valve, the o rings were okay, but the ball seemed stuck. Unstuck that, put it back. Then I opened the smaller one on the side (very accessibly located) and the half the o ring was missing. Replaced that, put it back, started the machine, but there was no difference.
Then I opened the bottom resolver for the bucket tilt valve, and the o rings in that were okay, but the ball was stuck as well. So I unstuck that and put it back. Tried to open the one on the side, but the allen head slipped. So I started the machine, and now when you operate the bucket tilt and boom lift together it lifts the boom, and when you operate the boom lift and bucket tilt together, it tilts the bucket.
So it's definitely better than it was, but I'm suspecting the second resolver on the bucket tilt. I'll have to remove the whole valve assembly to get access to that so it should be a fun job.
Anything else that I could try, or is the resolver the main suspect?