Linguix has a unique English dialect feature. However, it is crucial to understand how it should really work prior to assessing its quality. For example, for verbs very often UK spellings allows both using "s" and "z": sterilise vs sterilize, etc. Moreover, sometimes Oxford spelling may even prioritize "z" option.
Please, double check the suggestions. If you still believe the app has made a mistake, report it to us to help in algorithm training.