904 shifting problems

You could have internal pressure loss through worn parts that werent replaced, or you could have valve body programmign issues. Best way to tell is to have the pressures tested and recorded. Otherwise you're just making a ton of effort and shooting blind. If I had to guess, you have an issue with the high gear clutch or servo, or the reaction shaft/forward clutch retainer sealing rings. You can also try sticking a known good valve body into it to see what it does.