Awacatillo

Hello, I'm having a problem with my pokemons which is that they just disappear and reappear. An example is that about an hour ago I had a greninja on my computer and out of nowhere disappeared, another thing that also happened is that I had the garchomp of a friend said garchomp never took me alone appeared out of nowhere on my team, I wanted to know if they could help me with this problem that I have had for almost a week. For your attention thank you.