Good grip thanks to the rubber heel not so good, blowing one runs itself

Last year we had the Superfit ballerinas with buckle at the front. These were happy and also almost exclusively worn barefoot without any problems.
Today our daughter had after 2 hours of wear ballerinas back of the heel a dolle bubble. There is only a small piece of leather is incorporated in the shoe that bends slightly upwards and is thus uncomfortable to walk barefoot. So, this shoe can be worn with socks, for the summer so unfortunately nothing :-(