Thank you.
It's indeed a cache problem, because links generated by search page should open the image form it's parent album, not within the search page (breadcrumb shows "Search" instead of "TheAlbum".)
I tried a fresh 159 install : same problem.
I tried another theme : same problem.
I tried upgrading fresh 159 to 16a : same problem.
I cannot install 1.6.a from scratch : error in index.php
To make the link on a thumb work, I copy it, close the browser, open the browser, paste the link !
I did try under Linux, Firefox and Chrome, I did try under W11, Edge : same problem.
I did try to unset variables used in search page, or assign null to those variables : same problem.