Hi alfred,
There is no "sleep mode" in emteria.OS. And there shouldn't be any owl icons. Maybe it was a raspberry icon (same as in the settings)? In that case it could mean your CPU temperature is critical.
Please check the CPU utilization with your apps. If they generate too much load on the CPU and you don't provide appropriate cooling, the system will behave unpredictably. It may freeze or reboot or get slow and kill all the applications to prevent hardware damage. This explains the freeze you have described in another thread (I have removed it, since it is related to this topic - you are free to complain about the OS, but please try to limit it to a constructive criticism).
There were other sources of freezing (see
#310), but it should be fixed in the latest release.