Slip On Skate Shoes

almost like thongs do, the heel stays on the ground during walking and elevators and outside of the heel.

Noo, you need to find a good fit. If you talk about style skate shoes trainer, for example, Etnies, DC, etc., then you should definitely have a new pair of better fitting or tighten.
If you talk about Vans Classic Slip-on and then this happens sometimes, especially if they are old, or you can get on the wrong foot shape for them.
It is not so bad if you're just wearing them for everyday use, but if you wear them while skating, so it will be a problem and you can have an accident, in which case you should definitely get a new pair! : D
Hope I helped x

no