If the same ruleset assembly was present more than once in the current AppDomain, the game would crash. We recently saw this in Rider EAP9. While this behaviour may change going forward, this is a good safety measure regardless.
Make perfect mod ignore all non-combo-affecting hitobjects
Change difficulty adjust mod to match stable range of 0-10
Clean up HitEvents after use to avoid near-permanent memory retention
Fix crash due to unsafe mod deserialisation