You're right @aaronjensen96 - I've just booted mine, and it's struggling too.
The reason we had to temporarily drop the 4k support is because the judder was REALLY bad. It looks like even 2k is pushing the device to the limit this evening - possibly due to the HDR.
It's well within the supported specification from Google, which is why they're investigating why it can't cope.
I can only apologise, and hope Google sort something quick.
We'll have a chat within the team tomorrow about whether we need to temporarily suspend Ultimate support completely until this is sorted.
