FG-200B 5.2.6 performance descrease with errors in CLi and httpsd + pyfcgid in top

Hello all. I am facing troubles with my 2x FG-200B (5.2.6) in active-passive cluster. When traffic load rises, performance decreases dramatically. During performance decrease, there is 2 processes that appears(with several copies) most of time in the top utility: pyfcgid and httpsd. Also there is following errors appears(with several copies) in CLi: systraffic_stats.c:127:[1182]: ERROR '' systraffic_stats.c:127:[1180]: ERROR '' systraffic_stats.c:127:[1210]: ERROR '' systraffic_stats.c:127:[122]: ERROR '' Does anyone know something about this errors and this kind of behaviour ?