OJS 3.1.2.4 - problem with rebuildSearchIndex

Please note that these two threads deal with two problems.

The thread OJS 3.1.2.4 - Another problem with indexing and word search in PDF articles is about mis-indexing new PDF articles.

And in this thread I wrote that the “rebuildSearchIndex” tool removes words from the database that are already indexed.

Could the mysterious “Core :: cleanVar” be the cause of both problems?

Regards
Wojtek