Ok, my two children and I have played this game for a few hours today, and have observed the following issues:
1) Inventory items on my PC (host) slowly get messed up, as in they appear to be in between the item slots and I cannot interact with them or drop them out of my inventory. As mentioned with the OP, I have to restart my session to fix the problem. It is annoying, though, when you have this issue and you're the MP host and have to restart everything to clear up your inventory.
2) There appears to be an occasional Host/client update glitch that causes the clients to not see item/avatar updates on their end until they relog. This may be related to using and operating ships/boats/horses.
3) We've also observed the dismounting glitch with horses where control was lost for your character until you toggled 1st/3rd camera. This may be related to host/client latency, as we've only seen this happen with hosted games - I've never had this happen in SP.
4) We've also observed floating structures over the ylands, that appear to be metal and have electrical thingys on them, but not sure if that's by design or a spawn glitch.
5) We have observed cases where harvested trees leave remnants of their harvested materials far above the ground (and out of reach).
6) Lastly, we traveled to a nearby yland via ship (the 3 of us), and exploring the yland, I found and tamed a local horse, which then got head-planted into a mountain side. I mounted the horse, tried to back away from the mountain, only to find myself stuck in the mountain while mounted. I couldn't back up, dismount, or equip any tool (that's saved for another post - see feature suggestions), so I summoned one of my kids to come dig me out of the mountainside. As soon as they did that, I and the horse insta-died, and the game froze (clients as well - though they reported blinking landscape and still being able to move around their local area) as it was trying to load me back at my original land spawn. I had to kill the game process, and reloading it locked up again. after a 3rd attempt to reload the world in SP mode, I finally respawned, but could no longer interact with any chest/forge/etc to see their interactive GUI. I suspect that world is broken at this point.
I can provide screenshots and copies of files if you're interested in them. I plan on starting a new world at this point, preserving that one for debugging.