Hmmm…well…sorry, but I can’t comprehend what’s going on here - would you please help me to understand?
As I had never a plastic wheel of this generation in hands I’d really like to know if these are principially identical with the Strida 3 metal wheel version. Could you tell if the following technical details apply to your plastic wheels, too?
The flange of the pulley is not just a flange; actually incorporates this part also the brake drum.
The brake drum was secured inside of the hub (which is not separable from the pulley!) with six rivets:
One can see the heads of the rivets at the other side of the hub:
So, at least for my understanding, there is no chance for the flange to move - except:
- The rivets are broken (seems unlikely)
- The flange was separated from the drum “bowl” (seems even more unusual because this part is one massive steel sheet)
Besides of above mentioned: I think the flange can’t be pushed off the rear pulley - there is simply no room to do that.
Consider that the flange is extremely close to the frame - you need to see that vice-versa:
The pulley can be pushed of the flange (drum) - but not the other way!
However, even if there are zero rivets inside of your rear wheel should it still perform well (just the brake won’t work 
).
Inside of the hub should be bearings and a spacer, this parts again are secured by the wheel bolt (+ washers and locking mechanism) -
possibly there are parts missing or defective at the left side of the rear wheel…
