SUMMARY
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STEPS TO REPRODUCE
1. Load a short video with 'easy' object (I used the hang glider per Youtube video)
2. Find and add 'Motion Tracker' effect to clip
3. Change to ANY algorithm (I tried them all). No other changes. Click 'Analyze'

OBSERVED RESULT
Progress bar run normally. When finished a brown error dialog pops up saying '...failed to filter source'
Never gets to any keyframes but app does not crash.

EXPECTED RESULT
Per the many videos on YouTube, some copyable keyframes to inport to a 'Transform'.
Never gets that far.

SOFTWARE/OS VERSIONS
Windows: 10, 64b Pro
macOS: 
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

ADDITIONAL INFORMATION
A typical PC, Ryzen 5-3600, 32GB ram, 1TB M.2, Nvidia 1660Super w 6GB, etc.
The detailed log that I get after the brown error box starts out: 
"Current Frame:          1, percentage:          0
Current Frame:          2, percentage:          0
Current Frame:          4, percentage:          1
Current Frame:          7, percentage:"
and continues exactly this way until the last frame.

I'm just assuming this is a bug since I have tried many clips and algorithms and it always fails the same way no matter what I have tried. BTW I did read the manual and other bugs but I saw nothing like this. I have a screen pic but don't know how to get it to you, if you even want it. Or perhaps I am doing something wrong. Either way, thanks.