Raspberry Pi3b+ with piCorePlayer 8.1.0 looses ethernet interface

My setup is as follows:
I have LMS with my music collection on my home server.
I have a raspberry pi 3b+ with piCorePlayer connected to my LAN via cabled connection (same subnet as LMS server).
Audio output is via USB cable to a pair of Airpulse A300PRO speakers.
This setup works as expected, except for one annoying thing:
The piCorePlayer which runs on the raspberry pi loses connection after some time.
I can't trigger this, but the raspberry pi is always on and every morning I try to use it I find it with the connection lost.
I can't put the blame on the hardware as the pi was used before with volumio which ran well for weeks or months at a time.

So, if I attach a keyboard and monitor to the pi I can access the console directly.
If I issue an ifconfig command I get only the loopback interface shown.
if I issue an ifconfig -a command I get both the eth0 and lo interfaces shown.
If I try to bring up the eth0 connection with ifconfig eth0 up command, I get an error message saying: "ifconfig: SIOCSIFFLAGS: Operation not permitted"

So the only solution is to restart the pi either via command line or by interrupting the power.

Did someone else encounter this behavior? And if yes, did you solve this? And how?

Thank you for reading my post!