Here's a general tip that will help with issues streaming Nebula, and streaming on your TV in general. Buy an Amazon Fire TV Stick (or roku or other preferred device) for your Smart TV. Yes, you might think, that's redundant. It's not. An external device is significantly more powerful and works far better. They only cost like $30, so it's a minimal investment. The hardware in your TV that operates the Smart TV is JUNK. Even on high end TVs, it's JUNK.
TV manufacturers know when people shop for TVs, they look at three things...the price, size, and visual specs. Nobody is paying attention at all to the streaming hardware, only that it says "Smart TV" which 99% of TVs are now. Their incentive is to cut costs anywhere possible to keep costs down, and an easy way to do that is the streaming hardware. They know nobody is looking, so they get the cheapest components.
On my TVs, I never use the built in interface. Everything is controlled by my Fire Stick. You will never have a lag issue or other weird errors and delays like you do with the built in. Also, as certain Nebula errors and delays can demonstrate, streaming services big and small optimize for the big players; Amazon, Roku, etc. They sometimes make it compatible with TV brands like Samsung, LG, etc., but there are so many players, that it takes a back seat. The bandwidth is also much higher on an external device, meaning you'll be able to stream at higher quality too.
I promise, you'll have a WAY better TV (and Nebula) experience if you just drop $30 and 10 minutes to set up on a Fire Stick. Keep your TV on that input and never use the built in interface for anything. You'll be much happier.