Apple TV app judders/stutters on older (stereo-only) titles — but not newer 4K ones — on two Roku Ultras. Anyone else?

Hoping someone here has run into this, or that a Roku rep can weigh in.

I've got two Roku Ultras (latest gen, model 4850), each on a different TV, and the Apple TV app has had the same playback problem on both for months now.

When I play certain titles from my purchased iTunes / Apple TV library, the video judders and stutters every few seconds for the entire runtime. What's strange is how specific it is. It only hits older titles. Mama's Family episodes or the 1992 movie "1492: Conquest of Paradise" stutter throughout, while newer titles that stream in 4K play perfectly. The only common thread I can find is the audio. The affected titles are all stereo, and the ones that play fine are Dolby 5.1. So my best guess is it's something in how the app handles stereo audio on Roku.

It happens whether I start playback inside the Roku Apple TV app or AirPlay it from my iPhone/Mac to the Roku. Same result either way.

I've already worked through the usual troubleshooting. I've done a full factory reset on both units, toggled Match Frame Rate on and off, turned HDR on and off, changed the digital audio output format, and even dropped the app's playback quality all the way down to SD in the app settings. Nothing changes it. And since it's identical on two separate Ultras across multiple TVs, I don't think it's a bad unit or one specific television.

The frustrating part is that I've been through official support with both companies, and each one points at the other. Roku says it's an Apple problem, Apple says it's a Roku problem, and I'm stuck in the middle with no one actually digging into it.

It's my understanding that Roku keeps an eye on this subreddit, so if anyone from the team sees this, I'd genuinely appreciate some help — or even just confirmation of whether this is a known issue. And for everyone else, has anyone run into the same stereo-title judder? Did you find anything that actually fixes it?

Thanks in advance.