Sounds weird. First check, pop distributor cap, see if rotor can be twisted about 10 degrees CW, and it returns. Second test apply mityvac to vacuum advance pod, apply vacuum see If advance plate moves, and returns when vacuum is released. Then set engine at 5 deg mark, and observe if trailing edge of reluctor tooth is alligned with pickup sensor.
Cap, rotor, and plug wires are all new. Rotor also returns as it should. The pickup is gapped and locked down, and it aligns with the timing properly.
If you have not found a problem, put things back, T mityvac inline with vacuum advance, start engine, vac should be near zero with carb at idle, vacuum increase off idle.
Vacuum advance holds fine, no leaks, couldn't find my actual vacuum gauge though (still unpacking boxes)
Also check coil, see if blue wire goes to coil+, and green wire on coil- and no other connection there.
Coil wiring was fine, I tried swapping it as well
Also if using clamp on timing light make sure clamp polarity is correct, if setback light, set to zero, or try different light.
This is a cheap light I inherited and was having fits getting a good ground. After I got the car running well enough to idle as it does in the video, it looks like timing is going the right direction CCW when revved, but it's intermittent. It seems to be following heat/how long it's been running. The stumble and idle get more erratic as it warms up.