Some more specifics here could be useful to the devs - which settings are changing without you doing anything? I’ve never encountered that.
By rack system, you’re talking about the 4 kits? Kits and Instruments are two different things. Instruments are for Pads, Kits are for.. Kits.
While there is a lot of room for improvement,
(see my thread: Groove Agent 7 feature requests: For the Sound-Designer/Instrument Builder/Custom Samples User - Virtual instruments / Groove Agent - Steinberg Forums )
Groove Agent 5 is one of the top 5 most powerful, creativity yielding pieces of software I’ve ever used. It’s a sound-design powerhouse juggernaut for me. In my composition template, I have 4x Groove Agents, each with 4x kits of custom designed drum sounds (and other sounds.)
I would start just by loading your own sounds onto pads, and creating stuff… Learn all the features/ui to do with that.