Reported by email:

When MySQL 5.7.17 is running in group replication (a feature introduced in MySQL 5.7.17), all tables are required to have a primary key. Installing Piwik 3.0.3 on MySQL 5.7.17 running in a group replication settings, the replication breaks the group because all of the Piwik tables do not contain a primary key. The solution is to add a primary key to the three Piwik tables that do not contain primary keys:

piwik_log_profiling
piwik_plugin_setting
piwik_site_setting