Poor quality of service delivery

Channels 216 & 217 are supposed 4K images and are labelled “4K pop up” on the ultra decoders. What does pop up mean and why the picture quality no better than 1080i / 1080p? When using the streaming services on these channels, it’s no better and furthermore after a minute or so usage, the picture freezes (looks like buffering) and then continues - poor service delivery - why? For your technical people, all devices correctly installed, configured, setup and spec’d for 4K and I don’t get these issues with other service providers such as Netflix, etc.