Hello Marek,
How did you come to the conclusion statistics governor isn't working? Do you not see any update in update_time of SYSCOLSTAT or SYSCOLSTATS for the table (unless you manually called CREATE STATISTICS)? This is an indication of self-monitoring of statistics governor working.
The server checks statistics of tables that are loaded into memory, and flushes them every 30 minutes and checkpoint (self-monitoring). During the process, it updates histograms in ISYSCOLSTAT table and determines if statistics needs to be fixed.
Regards,
Jinwoo