Light bulbs constantly unavailable

I have 5x L510 & 3x L530 connected over three separate rooms in my house. 80% of the time, they work great. However, at least once a week one of the bulbs stops working. The app says it is unavailable and when you turn it on at the switch, the bulb flashes twice. The only way I can get them to work again is to do a reset (turning on & off at the switch for 10 times).

Can anyone suggest a reason as to why this could be happening?