With your suggestions I was able to downgrade to 5.3.2.1 with jbpatch installed.
Then, sadly, my first WiFi session pushed me forward to 5.3.7 again
I installed the bridge to avoid this issue, as suggested, and I got no errors during bridge installation. Maybe my fault was installing the bridge after updating to 5.3.2.1 and not before.
There is a way to know if the bridge is up and running? Now I will start over with Kubrick and so on... and I will keep my WiFi turned off until I understand what went wrong.
Thanks for your help