While brewing, I suddently lost all my temperature sensors (HERMS and Fermentation Fridges)
Here is my log: https://termbin.com/2x4d
I still have no life signal from them 
EDIT: They came back for a bit (5 min) but are gone again. My peak mem usage is around 81%.
OneWire devices are vulnerable to one of them being broken. If you unplug them, and then plug them back in one by one, it should tell you which one is causing errors.
I have tried already that but nothing changes
By the looks of it, you also have a DS2413. Did you include that when unplugging?
Yes I unplugged everything
To confirm: the Spark no longer suffers from periodic reboots?
Could you please unplug all devices, plug them back in one by one, and then run brewblox-ctl log? Connected/disconnected events show up in the log, but scrolled out of view in the previous log.
To keep track, you can also run docker-compose logs --follow spark-one. This will open realtime logs on your device.
Since the last firmware update I think it doesn’t reboot anymore. Let’s see how it behaves today during brewing. But the memory usage drop quite a lote so let’s see.
The thermometers came all back again now. Let’s see if they stay otherwise I will follow those steps.
Intermittent loss of all sensors suggests an electrical issue in one of the devices that causes a read error.
Indeed do please let us know if the problem reoccurs.
Last brewday it didn’t happen again but today is happening again as well. Suddenly all the thermometers are gone. Regarding the reboots it still happen but way less often.
Could you please run brewblox-ctl log?