apache doesn't start asking to recompile PHP

I’m using Webmin 1.821 with Virtualmin 5.04 GPL on Ubuntu 16.04, just reinstalled after some storage troubles.

I reimported all my websites but now I have a strange problem:

If I enable apache mpm_prefork, run it as www-data and run mod_php the old way everything seems to works but I have a lot of troubles with websites.

If I try to switch to the modern mpm_worker, run the website as domain owner and using php7 as fcgid
apache refuse to start with the error
Apache is running a threaded MPM, but your PHP Module is not compiled to be threadsafe. You need to recompile PHP.
I have php 7.0.8 (automatically installed with the virtualmin install script).

I checked the homes permissions (and are ok), I checked the php configuration files and the handler entries are commented.

Can you help me to switch to the “new” apache threaded mode?