This issue has been updated, the real problem is as follows:
I have added some new terms with the following keys:
custom.pae.services
custom.pae.services.1
custom.pae.services.2
I have cleared cache.
The server has crashed (error 500 Internal server error).
@microstudi (https://github.com/microstudi) can give more technical details, but the problem is that according to the YAML format, a key (custom.pae.services) cannot have assigned a value if it has child keys (custom.pae.services.1). Since a user like me is not aware of this restriction, it is necessary to have some kind of validation that avoids this behaviour (otherwise, any admin user can crash a Decidim by adding new terms).