i have just bought a YN 460 ii and it fired fine at full power for about 10 pops then the pilot light just flashes red and green . I switch it off for 5-10 mins and it works again fine for another 10-15 times. I have read that there is a QC issues with YN and this might indicate that it has overheated. Has anybody else had this issue or know if it can be resolved without replacement. People have suggested batteries maybe an issue but mine are brand new and fully charged.