Context for my experience: I've been using Vuforia for awhile, successfully. I understand how it works, generally, and I've done three projects now using it.
The project I'm working on currently is having some issues with Vuforia. Tracking is inconsistent and has not been stable at all. I'm unsure what I've done wrong, and would appreciate some help troubleshooting this.
While tracking an image (this happens successfully), the model placed on the image is not being properly rotated or positioned. It feels as though it loses tracking every couple frames. I'm using a simple Cube right now to test, so the geometry is minimal. My tracking image that I'm using is also 5 stars, so that doesn't seem to be the issue either. I've tested this with several images that I've used in the past, with all the same results. I've also tried increasing the frame rate of the camera to stabilize the tracking consistency, thinking that it just wasn't fast enough for my phone (Google Pixel 4 XL), and this caused jittering and did not improve tracking. I tried enabling VSync, but saw no difference.
This is a VERY simple setup and does not have any niche properties. I tried following a tutorial for Vuforia in a new project, updated to 2020.9, and saw the exact same problem. I installed Vuforia using the link from the Downloads section, which leads to the asset store. I then imported using Package Manager. I have Git installed on my PC.