whoosh backend still not working in version 4.28.
As already described in the related issue #1096, the problem still persists in mayan version 4.2.8.
After upgrade from 4.2.4 without errors, reindexing search index yields to the known lock errors in the log. No topics could be found by the whoosh search function. Installation is the same as described in the related issue. Switch to slower database search, which works, at least.