
While I can't explain the cracking sound, the spinning is completely normal, there's an oring in there which compensates for the tolerances of various components and it's job is to be compressed more or less so in some cases the oven part resting on it might slip over it, doesn't affect anything.
Also, wanted to say, after this has been pointed out to me, I apologize if I come out as crude or even rude at times, I promise you, in no case do I mean anything bad in any way. It's a language and cultural thing. I mean Serbian has the most swear words of any known language so there's that.