I traveled to Japan last Summer and noticed many vending machines had problems with the new bimetallic 500-yen coin.
Must be a huge headache upgrading all those machines. But then I can understand you'd want to keep the 500-yen coin hard to counterfeit since it's quite high-denomination.
It is not just vending machines. I have had the new 500-yen coins rejected on buses, in food stores, etc. It will happen gradually, but I think it is the first time in my 15 years of experiencing Japan that there has been any change to a coin so I expect it to take at least another year.
Must be a huge headache upgrading all those machines. But then I can understand you'd want to keep the 500-yen coin hard to counterfeit since it's quite high-denomination.