Hello antonin can you share more pictures about your configuration I have the same problem . my configuration is similar like your configuration
KUKA:
Robot: KUKA KR 6 R900-2
Controller: KRC4
Firmware version: v.8.5.7
Workvisual version: 5.0
Profinet: KRC 4 Profinet 4.1
Option Packages: Diagnosis Safetyy v3.0.0
SafeOperations 3.4.6
KUKA PROFINET M/S (V4.1.2)
Siemens:
TIA Portal: V15 sp1
CPU: 31513F-1PN
DI16*DC24V
DO16*DC24V/0,5A
kind regards