Every since the first event; Halloween Event, a glitch allowing trainers to get double candies for walking their buddies was first discovered. At first, it was thought to have been a simple missing distance calculation with the decrease in distance walked. It took the game longer to credit trainers for the distance they traveled. When the Pokemon Go did update its distance, trainers received two candies for walking because they walked the distance for two.
Though, after the Halloween event ended, this bug never seemed to stop happening. In fact, more trainers were reporting the glitch worked for them. Recently, we have been seeing an increasing amount of work being done to the game, fixing mostly bugs and “minor text fixes”.
The double candy glitch is a welcomed bug in the game, unlike many other bugs, but like others, it’s expected to get patched at some point. Thankfully, trainers are still receiving double candies.