Notes Station saturates memory

[Murrey]

Hello all
I would like to know if you have the same issue on your Qnap filers.
I observe for few days a strange behaviour from my Qnap TS-239 Pro II. Memory is saturated by Notes Station. I precise Qnap is at latest firmware (4.2.6 build 20171026) and Notes Station is in version 2.1.53. Physical memory is increasing until physical memory is full.
I have another modules which are running with notes Stations: Surveillance Station, Phpmyadmin, IPKG, Teamspeak, Cloud Drive Sync, LogitechMedia Server, JRE, PhpMyAdmin. I have tried to close some module and it seems that Notes Station and Surveillance Station (NRVD) are consuming memory together.
- If I keep Surveillance Station running without Notes station running , free physical memory is stable at 430 Mb
- If Surveillance Station and Notes station are running, free physical memory is full after 2 ou 3 hours
- I haven't tested yet Notes station running withou Surveillance Station

Filer was running fine for months or years. I'm asking if latest QNAP firmware is not the root cause. Is there a way to roll back only Notes Stations in 2.1.51 for exemple ?