I have this same issue on an S5. The logs fill up with ~85MB over several days, filling the device entirely. At that point, the S5 shows as being on the network, but is basically inoperable.
There are three ways I've found to get the printer back into an operable state:
1) Factory Reset
2) Cura Connect Reset
3) SSH into the printer, and clean the log files directory, then reboot the printer (via the CLI)
Once one of those three steps is taken, the printer will be operable again for between 2 and 10 days, at which point the cycle repeats.