When using the oXygen plug-in (in combination with Checking Profiles ), an unassigned rule set may not be saved after checking. Instead, the checking options will default to the previous ruleset the next time you go to check.
This behavior can occur if a ruleset is not assigned to any of your Checking Profiles.
To avoid this, create a new Checking Profile with the desired rule set associated with it. The oXygen plug-in can then save the ruleset in your check settings, preventing the need to always select the rule set for subsequent checks.