"My five-year-old is crazy about mixer truck and he really loves this toy. It’s not very hard to build. He built it mostly by himself and it worked! The mixer truck can function perfectly. But after he played it for an hour or so, the mixer truck now can not move forward. It can only move backwards. The drum works ok. So I think the issue comes from the back wheel. I guess he ran the truck too quickly and then something got wrong. Now the question is do we have to rebuild it from the scratch? The wheel powering part is among the first 25% of the progress. This is very frustrating. He kept asking me to buy a new one:-("