Horses despawning and game crashing quite often

I had 6 tame horses including 2 skeleton horses all with saddles and/or armour which were all in a secure place (couldn't have run off) and now I only have 1 skeleton horse. This is very annoying and I think should be fixed.
There is also another bug where every 5-10 mins the game will crash which has been the cause of missing items.