I had a similarly manifesting issue with a Marantz RC5200 for which I never found an answer. This one was worse -- some time between one week and six months after programming the remote, it would revert to no program. I never could work out what was wrong, but several of us suspected some commands had been learned in a squirrely way that affected the remote. You may have a similar problem.

I relearned and relearned, never solving the problem until I changed the remote to a newer version that used different logic chips and different software, and so, in a completely random manner, was not susceptible to the problem. Which is still there.

I'll be you have a strangely learned command in the remote. First thing I would do is relearn the commands for the products that are involved in that macro. It's a complete balls-out sin that URC's sotwere doesn't let you look at the hex code here. There's software we could use to take learned codes, deduce their base information, and create perfect codes with zero errors or squirrelicity. You could always get an old Pronto, squirt the codes via IR out of the URC, learn them on the Pronto, then investigate from there, but that's another opportunity for a bad learn.

Best of luck. This is a killer.