I’ve had quite a long discussion here regarding 5.1.6 vs 5.2.2 (Error using PostgreSQL as database backend with Gramps v5.2.2 - #14 by UlrichDemlehner and Performance Issues with GRAMPS - #16 by UlrichDemlehner). The problem with 5.2.2 is that it does not support the BSDDB backend anymore but without the BSDDB backend, my database (100k individuals, 250k events) is simply to slow to work with it.