Upgrade from 6.0.9 to 6.0.16: getEnableAppBuilder() error


I’m using docker to run Open Suite 6.0.9, but I’m pretty sur my execution environment is unrelated to difficulties I get.

My current try :
_install of 6.0.16 in a new container, and link /var/lib/postgresql to a copy of files used with 6.0.9 (which is equivalent of using the database working with 6.0.9 with application in 6.0.16 without docker).
_starting the container (database + webapp)
_authentication with admin account

First I got getEnterpriseCommunication() error. The fix described seems to get ride of the error.

Now I got a new error : « Cannot invoke method getEnableAppBuilder() on null object ».
I’m stuck to this point, and have no display of the applications menu.

Any advice on a better way to upgrade (with or without Docker) ?
Any solution to solve the getEnableAppBuilder() error ?