1.9 sword dissapering

i think its a kind of bug in mc 1.9 becouse sometimes my sword dissappears in my main hand and i cant blockhit with it also the sword doesnt do damage and only knockback (also the axes do a lot more damage) and i think its a kind of bug becouse it will ruin the whole pvp system and some servers that are only for pvp and it is very very annoying and i will ruin the whole 1.9 update
THANKS FOR LISTENING TO MY OPINION