I tried this, but don't work like I thinked. When jackett need more memory, and this makes it exceed the 400Mb of limits.slice, only jackett is reboot, not sonarr or radarr like I thinked (and jackett can't update).
But, for what I saw, even 300MB isn't enough for update v0.11.15 (released today).
Jackett updated to 0.11.15 here, but nuked my RPi3 first
I will see what I can do
But not now