PMS keeps stopping on Synology 1511+

Hi, I'm new to this forum. I hope someone can help me.
I've got the latest version of PMS installed on my Synology 1511+ NAS and also on my MacMini.
The PMS on my NAS keeps stopping every two or three days and works fine when I restart it.
I have no issues with the PMS on my MacMini which reads the same NAS folders I've mounted on the MacMini. (I use this solution as Roku Plex client works better when MacMini does the transcoding.)
Any ideas as to why the PMS on my NAS keeps stopping?

Thanks
Merim