dkcarmona , 99mb should be plenty to stream. The problem (in descending order of probability) could be:
1. Roku's poor software development. There's so many software problems -- and apathy or hubris from the company -- that this would be first explanation to reach for. (The "boy who cried wolf" phenomenon. The obvious disregard Roku has for its software. Just a couple weeks ago, at the height of people complaining about how their antenna tv was broken by the latest untested update, Roku changed at least my screensaver to a broken antenna tv. It's like they're proud. They certainly don't care. There's problems that have existed for years.).
2. Your 600/600 internet service my have quality issues? That definitely happens, and has been a big problem the past year of lockdowns, etc. You should check your speed & latency.
3. A wifi issue? If your tv is connecting to 2.4g there could be congestion issues (interference from other devices, neighbors, etc.). If it connects to 5g, and the router is a large distance, that could be an issue. (Not the reported speed, which sounds ok to me. But, quality of signal. dropped packets.).
I'd put my money on #1. The quality of Roku's software is flat-out bad (unstable, bugs not tracked, updates not tested).