Here's a particularly odd one...
If my Magic Guard Clefable has to use Struggle, it completely negates Magic Guard for that turn, as I took my 25% from Struggle (normal), but then proceeded to take over 50% from Poison damage (wrong!) and another 6% from Hail damage (wrong again!). Probably just a problem with Struggle removing Magic Guard's protection for the attack, but not putting it back on after the struggle is resolved.
If my Magic Guard Clefable has to use Struggle, it completely negates Magic Guard for that turn, as I took my 25% from Struggle (normal), but then proceeded to take over 50% from Poison damage (wrong!) and another 6% from Hail damage (wrong again!). Probably just a problem with Struggle removing Magic Guard's protection for the attack, but not putting it back on after the struggle is resolved.