This thread is for common glitches and issues, and so that you can maybe find a fix for them. If you have issues, try to find it here, and maybe you'll find a solution. 

The Random supersonic teleportation glitch

Well, the title makes it sound more exciting than it is.  Basically, your blockhead randomly zooms to another spot a few thousand blocks away. It leaves a trail of uncovered spots in the fog of war darkness.

FIX: No real fix, and currently no known triggers yet. You might just have to walk back. If you're REALLY lucky, maybe catch another one of these back 

The double-placing glitch

Basically, if you're on a laggy world and you place something but it doesn't load up yet, and then you place something else there while it's loading, two things could happen - one of the things will drop, or one will disappear.

FIX: Unfortunately, if it's gone it's gone. Avoid doing this, and wait until the thing loads before doing anything else.

The North Pole Handcar Glitch:

You're riding your handcar past the north pole when suddenly your blockhead disappears. You jump off of your handcar and find that the handcar you used can't be used anymore!

FIX: I've heard people say that if you don't get off your handcar and crash the handcar into something instead, you will still be able to use your handcar. I haven't confirmed it yet.

A strange type of world corruption

Your world gets corrupted! It's a weird, and unfixable glitch that does a lot of weird things, including:

-Things turning into level one workbenches that are UNUSABLE
-Items randomly turning into golden chests
-Upgraded portals and workbenches going back to level one

FIX: None that I've seen. It appears to be, unfortunately, world corruption that can't be fixed. You can try to use the items in the golden chests if you can get into them, and you can also try to salvage the materials from some of your old structures. You can move to another part of your world IF POSSIBLE (It might not be, there might be too much damage, or things might be weird in this world forever), or, if your portal chest works, which it might not, you can try to move your items to a new/other world. If not, then unfortunately you will have to start all over from scratch.  Good news is that this is very unlikely to happen. I've played this game for quite a while and I've never had this happen to me.

The Door bug

Your blockhead for some reason decides to climb over a building instead of walking through the doors! This is most often caused when the inside of the building isn't properly or completely loaded, however this is not permanent and will not damage your world.

FIX: Tapping inside of a building seems to work in most cases.

The elevator isn't working!!!

Sometimes, when you place your elevator motor, the elevator doesn't work properly!

FIX: Try picking up and replacing the elevator motor.

The Walking glitch

You've told your blockhead to walk somewhere and you exit the game. When you come back in, your blockhead is walking on the spot!

FIX: Although it is annoying, you just make your blockhead walk there again. Sometimes this will happen again when you exit the game, so you may need to repeat this a few times.

The Donkey bug

You try to mount onto a donkey. When you mount on, it looks like you're siting on the air!

FIX: No worries, nothing bad happens, just get off and mount the donkey again!

The Background Item Glitch

For whatever reason, sometimes wire/chests/ladders/torches/lanterns will not work properly anymore, and will become the background., and it will work and behave like the background, so you won't be able to interact with it anymore, because it will be background.

FIX: Try removing the back wall if possible by removing the block (don't use a pickaxe or you might lost the chest), if you're in a cave or for whatever reason can't remove the backwall, then try pouring water over the glitched item, sometimes that will work and fix it. Also try to place a bed over ti and then sleep in the bed, which has worked in some cases. If that still doesn't work, then I don't know any more fixes, you can place items and blocks over the glitched item if you wish to do that.

NOTE: Torches and lanterns affected by this glitch will continue to produce light, however they can't be removed properly. Ladders, chests, and wires affected by this glitch will not work at all, you can't open the chests, you can't climb the ladders, and the wires won't conduct electricity.

The Hungry Freight Car!

Okay, so apparently, your freight car got hungry and ATE THE ITEMS YOU PUT INSIDE!!! (Mmm, delicious steel ingot!) In other words, items that you put in our freight car disappear when you open it!

FIX: Sadly, your items are gone. No fix.

The Corrupted Area

Sometimes, your game crashes whenever you look in a certain area. Most or all cases have occurred on Cloud servers. Everyone on an affected server is prone to the issue as far as I've seen.

FIX: No fix known yet, just try not to look in that area, though the rest of your server should be safe. If your blockhead somehow gets into that area, your game will most likely crash every time you enter that server.

The Unknown Glitch

There's a regular-looking item in your inventory…and it's called "UNKNOWN" instead of the item's name, and it doesn't work like the item, but it works like your hand! Sometimes, you'll see "UNKNOWN" time crystals…in your inventory!

FIX: No fix for those items, and it's currently unknown what's causing the issue.

The Boat/train with a mind of it's own...

This glitch happens on multiplayer, especially on servers with lag. You get off your boat, handcar, or train, but the vehicle keeps moving!

FIX: Just chase after it. Often you'll find it spinning around in circles, which is a bit odd. It should still work though