We use several parameters_*.yml files based on environment and load a single parameters_base.yml file to avoid duplication of config settings. It seems ParameterHandler doesn't import this .yml file before comparison. Thus, it thinks there are settings that are needed, when they are actually set by the included file via the imports method.
Our parameters.yml:
imports:
- resource: parameters_base.yml
Could the imports/resources be parsed for additional config settings before the comparison?