The issue is reproducible in browser emulators and on real devices.
Steps to reproduce:
- As a user who's never seen the intro tour on Special:Search page, go to https://en.m.wikipedia.beta.wmflabs.org/w/index.php?title=Special:Search&fulltext=1&ns0=1&profile=default&search=cat.
- The search results will be displayed without thumbnails - CORRECT.
- Perform horizontal scrolling - the intro tour "Search Result Previews" will be displayed.
(click on the anumated gif)
Once dismissed, the horizontal scrolling will be gone; users will not have access to QuickView features - all works as expected.