I wasn't saying you're playing on a low-end device haha, just that performance on lower-end hardware is something I still need to work on too. But I think I just figured out what's causing the camera jitter! The camera interpolation runs in _process(), while the player movement runs in _physics_process(), so the different update rates might be causing the jitter when FPS drops. I'll try to fix that in the next patch!
Thanks for your feedback! This one was really hard to catch because it never happened to me haha. Thanks again!