Yeah i have no idea how to reproduce it reliably, though if i can record it happening a few more times, maybe i'll find something in common between the cases?
I did notice when trying (and failing) to reproduce the bug that diagonal edge panning doesn't work the same on all corners (on my end, at least).
Specifically, moving my mouse to the the lower-right corner of my screen makes the camera move right only,
but placing it further left makes the camera move down-right correctly.
When using the non-modal UI, the point where it switches between "down-right" to "right" is somewhere below between the letters i bolded in "Adv. Component Analysis Suite" when one is in inventory.
I'll get back to you if i find enough occurrences to figure out anything more.