The cause for so many hackers recently is because a hack creator developed a new method where it injects the hacks through a website into the game. Anyone who has paid for the hack can inject the hack into anyone in the server, even if they haven't downloaded anything. This is only recently getting sold and that's why there's so many people hacking.

To make it so it doesn't drop, you would have needed to drag the blaze over the repeater instead of repeater over blaze

This happened to my friend. My friend was picking up the barrel but then another one of my friends opened the barrel at the exact same time which caused my first friend to have the barrel stuck in his hands permanently.

Probably invisible fireplace. That happened to me once

This happened in my inventory also. Basically what happened was I used an item from my med kit but it glitched and stayed in my inventory even after it wasn't there (just continued to say "Receiving..." when I right clicked it because it didn't really exist there anymore), and so there was REALLY one more free slot under it (because med kit is 2x2 slots), I then created a splint and because the med kit is 2x2 slots, it thought I only had one more free slot vertically, but really it had two (but the top slot was being used by the glitched item), so it still put the splint there and made the med kit glitch and have an extra slot downwards.