How to reproduce:
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Create a fresh Firefox profile
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Install UI.Vision from the Firefox Add-ons store
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Open this example link:
https://www.hltv.org/matches/2388127/furia-vs-natus-vincere-starladder-budapest-major-2025 -
Scroll down to the Highlights section
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Click the first highlight:
“M1R1 | w0nderful – 4 P250 HS kills on the Mid to bombsite A offensive (initial 3vs4 situation)”The page scrolls down somewhat sluggishly and opens the video player after a few second delay. It’s normally smooth and instant.
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While the video is playing, click another highlight, then another, a few times.
What happens:
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Initial highlight click open the video after noticeable delay (Step 5)
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Switching between highlights is noticeably sluggish (Step 6)
Important note:
If I uninstall UI.Vision and repeat the same steps, everything from step 4 onward is buttery smooth — no lag at all.
I work at a computer shop and tested this on many different PCs (different CPUs, GPUs, operating systems) with fresh stock Firefox installation. The issue reproduces on all of them, so it doesn’t seem to be hardware or OS-related.