Potion effects

Sometimes, if I try to put potion effects on me or my friends, they don't work and they seem to glitch a bit when using the /gamerule command.
We tested it a few times and found out it was quite common for us, not sure about anyone else though. Could just be us doing something wrong but someone suggested posting. So anyway, if I was changing the game rule using things like doTileDrops False, and I try to put effects on my friend they wouldn't work, they would show on the effects but wouldn't work.