Question Image tracking doesn't get updated after initial detection on Android

Image tracking doesn't get updated after initial detection
When using a MutableImageLibrary, after adding an image to the mutable image library and pointing the device camera to the tracking image, it gets detected. But subsequently it will not detect any changes in movement. This mainly happens with smaller tracking images, around the size of 3 by 3 centimeters. The tracking images themselves are QR codes. Larger tracking images, also QR codes, suffer the same problem from time to time but not as frequently.

In my code, I use ARFoundation's ARTrackedImagesChangedEventArgs struct to handle the detection, updated and removal of tracked images. The ARTrackedImagesChangedEventArgs "added" event gets received almost as soon as I have the image in view, which is great. But subsequently no ARTrackedImagesChangedEventArgs "updated" events are received unless I move the camera up and down and around the tracking image. Once the tracking image has been "updated" in this way, tracking seems to be fairly stable.

What could be the cause for this delay in "updated" events? On physically larger tracking image, also of QR codes, a slight delay sometimes happens as well, but not as frequently or annoyingly as the one for smaller tracking images. Changing the expected physical size to the physical size of the tracking image when adding it to the mutable image library doesn't seem to help alleviate this issue.

On iOS devices tracking proceeds as expected, with the "added" event being followed up with the "updated" event almost immediately even when tracking smaller tracking images. Any help or insight for this issue is appreciated!

Additional information
Builds were tested on these devices:

Motorola One Macro, Android Version 9
One Plus 5, Android Version 10

Builds were made with the latest versions of the AR Foundation & AR Core packages, and build on Unity version 2019.4.6f1