Everything was great - except for the wheels

I have the chair for half a year and it's all very well - except for the wheels. Reportedly, the hard floor wheels that come - but they come for me not soft enough before. Have used it on a sisal rug, which it has promptly "eaten", while the wheels of the beginning "bucked" and blocked from me incomprehensible reasons repeatedly (if you turn the stool and the wheels individually turns everything goes). The problem I have ignored until now not only the carpet is broken, but broken and the first wheel. I got the wheels from the outset but can not get out (she wanted to replace it with soft floor casters), and even now, when I try to play with more vehemence, the pins remain steadfast in the chair and I know no solution. Only one star deduction, because I do not know to what extent it is up to me, and to what extent there is a problem in other swivel chairs - otherwise there would be more!

Update: I have now the manufacturer (Versee) contacted and get competent answers. The pin I eventually figured out as a lever with a chisel and finally bought soft floor casters (there are in the eBay shop of the manufacturing company and on its website. Pin is actually 11 mm.) I'm curious times, whether they are running properly.

2. Update: Wheels are now the correct, "eat" no longer and run better - although still not 100%. With my old chair that was not so good, I had no such problems. I just now but resigned and got used to that it makes from time to time ...