Aha, at the first read I thought it is related to device specifications. Now I can also reproduce the problem.
Alternative description: searching with the Search box in the top-right corner (the one which is present on every FN page) seems to die when searching for (many? most? any?) device models with simple numeric identifiers (6255, 6600, 6630, 3250, 3650, just a few I have tried).
Some letter+number identifiers also trigger the bug. 6310i, N80, N91, N93 and N95 do not work, while N93i and N96 work for example. Complex names also seem to work at the first glance (the ones with -00, like N8-00, E7-00, but I have not tried the others)
Only the box seems to be affected. The "Please try again" text links to
https://www.forum.nokia.com/search/, and re-typing the query there (into the form) brings correct results. Re-typing the query into the top-right box repeats the bug.