Dragon Death Effects Keep Going

I wanted to test the ender Dragon death effects (the light beams), so I /summoned an Ender Dragon with no health. I noticed that for some reason, the effects keep going instead of vanishing, and they grow larger and larger. The only way I found of stopping them is /killing the Dragon, which for some reason is still "there". I hope this will be fixed soon. This only refers to a /summoned dragon- the one in the actual end works perfectly, except for another unexpected flash of light after its death. Here are 2 pictures of the light after growing too much.