Dropped frames

The encoder produces frames faster than the upload can carry them, or faster than the machine can process them, and the surplus goes in the bin. Everyone watching sees the stutter. OBS reports the count in its stats panel and YouTube flags it in the Live Control Room under stream health. Blaming the internet is the first instinct and it is often right, though an overloaded CPU or a busy GPU produces the same symptom. Work down the dull list: a wired connection instead of wifi, a bitrate the upload can actually sustain rather than the one a guide recommended, then a lighter encoder preset.