There seem to be a lot of weird bugs lately. I've reinstalled the game maybe 5 times in the last two weeks, but it just keeps the problems at bay, doesn't solve them. I suspect a memory leak, or something similar.
Sometimes my buddy pic disappears. Sometimes the weather disappears. Everything else works normally. And sometimes all gyms, stops, and external pokemon disappear, but I can still use potions, send gifts, etc. Weird.