Hi @suisse,
Well, it was long... it took 2.5 hours of testing and measurements on the line. There was too much noise and errors in the internet connection. Errors that the devices (IB3 and the central network card) could correct. However with the high traffic generated by the PS4, the devices could not cope with the high number of errors and and the IB3 restarted the internet connection, with the port at the central network card going into error mode requiring 15 mins to restart.
In order to correct the errors on the line, the technician did:
1. Replace part of the telephone cables, from the entry in the house till the back wall socket.
2. Replace the wall socket, the one fitting the violet DSL cable.
3. Replace the IB3 (under warranty), probably not necessary.
Since yesterday evening the network at home is back to normal, PS4 on, connected via Powerline, without problems. The line is being monitored for 24 hours to check the quality and stability.
Thanks for your support, I will share in case the issue comes back.