When using /cam follow entity @e[type=zombie,limit=1,sort=nearest] (my instance), then adding points, two things can happen:
- adding points through cam add (first being 10 4 -10 and second being 15 5 -20)
the scene still works when played also (video of it not sent, no issue)

- adding points through pressing p
This looks normal, but when played

This happens:
https://0x0.st/8YaC.mp4
Notes:
Cam target is targeting the zombie in the glass box
Cam mode outside is on
circular interpolation. it seems that the second point factor, or first is multiplied on the X and Z axis, Y is neutral