Poor ground at trunk back light bulbs liftback

Hello, I'm trying fix my issue that is bearly light in trunk when lid is open. What I check till now:

1. I have changes trunk lid lock to new one, connectors 3pin are fine, and I see open trunk info at MaxiDot

2. I have checked connector at left C-pillar, there Is black/brown cable that has ground when lid is open, and ground disapear when lid is closed

3. When I disconnected 3pin wire from lock at lid, I still have about 9-10V at trunk lights connectors

4. When I put healthy ground to the bulb, it lights normal

5. Resistance beetwen healthy ground and faulty ground at lid light bulb connector Is about 20 kOhm

6. I have checked that ground signal from trunk lock do the ECU is providing only MaxiDot info

7. What should I check to find faulty place where ground cable could be damaged ?

8. Ground cable from trunk lid connector goes to the major wiring in trunk but It seems to be not the same ground line that is disconnected by swith in trunk lid lock

Im sorry for my language, If it is something hard to undestand, please ask. Thanks for your time.