When I was teaching many, many years ago, I told my students that there is no such thing as a dumb question, but here goes.
We are using Firesticks with mine being the Max.
I use Tivimate with an an unverified IPTV. I am using IPVanish out of Miami. We get buffering on ABC out of Orlando (news and my wife’s channel) and Bally Sports Detroit (BSP) all the time. I’ve seen times when there is voice on BSP, but no picture, and the vice versa. Some of the time it is jumpy. We get around 150 Mbps with BlueStream Fibre with IPVanish on. I’ve rebooted and changed IPVanish servers to no avail.
We see next to no buffering on any other channels.