Found a bug; replay checks don't work properly on Flexi-packs.
What's actually happening here is, there's an option (not listed in the Flexi Toolkit, but it's available by modifying the SYSTEM.DAT file through the NeoLemmix Editor's SYSTEM.DAT editor) to enable or disable the replay checks. The Toolkit always sets this object on. However, the player interprets it as the opposite of whatever it's set to - so the option works, but it's treated as "off" when it's on, or "on" when it's off. So, all that's needed to fix this is change the name of it (in the editor's SYSTEM.DAT menu) to "Disable replay checks", and set the default to off instead of on. In the meantime, to get replay checks working for custom packs, simply use the NeoLemmix Editor's SYSTEM.DAT editor and turn that option *off*.