I have done as much as I could to make this mod bug-free. My mod runs perfect for the most part, however there are some slight issues that may occur that have to do with Skyrim's engine and I can't do anything about them. Here are some workarounds if you encountered any of these issues:

IMPORTANT: Always make a hard save before building anything. Once you've built it you can't disassemble it, and if you were positioned wrong or chose the wrong options, or something went wrong with the building script, you have to load the save file.

Problem: Dropping the shacks or furniture does nothing.
Cause: Skyrim's scripting engine is too busy.
Workaround: Pick the item up and drop it again.

Problem: You get a “Can't build while in combat” message even when you're not in combat.
Cause: The game for some reason thinks you are in combat. Some NPC is chasing you from far away etc.
Workaround: Wait a while, go to a different location, find the NPC that has aggro on you and kill it, etc.

Problem: Some plant, tree, or rock is clipping through the shack.
Cause: Things generally clip through in Skyrim if you placed them inside each other.
Workaround: Either load the save and build your shack somewhere else, or use console commands to disable the clipping object if it's not important. (more info in console commands section)

Problem: Player collides with invisible objects inside the shack.
Cause: This is a problem with Skyrim's engine not updating the location of the objects' collision data
Workaround: Go to another interior place. Save the game. Quit Skyrim. Run Skyrim again and the issue should be fixed. This issue will generally be fixed on its own and only happens once, so you don't have to keep quitting Skyrim.

Problem: There are two of the same object inside the shack, and one of them is right in the middle.
Cause: This happens very rarely and seems to be an issue with Skyrim's engine.
Workaround: Reload your save and build your shack again. This issue happens rarely and usually won't happen twice.

Problem: After building a shack at a height, you fell from the shack before making the stairs and can't get back into the shack to make them.
Cause: You were careless.
Workaround: You have several options:
-Load your save file, build the shack again, and be careful not to fall.
-If your shack was marked in the map, fast travel to the marker.
-Use console commands to fly back into the shack. (more info in console commands section)

Problem: Furniture placed in the wilds is either too much in the ground or floating in air.
Cause: Skyrim's furniture are only made to be used on flat surfaces, and the surfaces in the wilds are mostly not flat.
Workaround: You have several options:
-Find a more flat surface to place your furniture.
-Use a plank to create a flat surface in the wilds.
-Use console commands to tilt your furniture until it looks right. (more info in console commands section)

Problem: After placing a furniture in an interior, the player is transported into a void.
Cause: You were facing the wall when you placed your furniture. You should be facing the room.
Workaround: Load the save file and place your furniture when facing the room.

Problem: Marking a new shack on the map causes the previous markers to disappear.
Cause: The total number of map markers are limited. You can mark up to 25 shacks, 10 tents, 16 chests with fast travel and 16 chests without fast travel.
Workaround: Only mark the locations you think are necessary to be marked.

Problem: NPCs can't seem to find their way around the shacks and other furniture.
Cause: Since these items are placed dynamically in the world, they can't alter the “Navmesh” information that tells the NPCs where they can go. However from my testing the issues are minor as they seem to be a bit confused but they find their way eventually. Sometimes if it seems they can't go where they want to go they just “pop” into the correct position after a while. While this can be immersion breaking it doesn’t happen often and ensures the game proceeds correctly even if the NPCs can't find their way.
Workaround: You have several options:
-Make sure you don't place the shacks in the middle of the roads or other places NPCs use regularly.
-You can try building your shack high up in the air so the NPCs can walk under it.
-Use the “Burrows and Basements” instead of the shacks. These will only add a trapdoor to the world that the NPCs can just walk over easily.

Problem: The location of the rest of the merchants is not known.
Cause: I'd prefer it if you discovered them on your own. :)
Workaround: There are 5 carpenters. One for North, South, East, West, and Center.
North: Dawnstar, The Mortar and Pestle, second floor.
South: North of Helgen, close to where the player will be when the first quest is done.
East: Darkwater Crossing, Goldenrock Mine, down the first corridor.
West: Karthwasten, near the entrance of Fenn's Gulch Mine.
Center: Whiterun, Warmaiden's, on your left.

Problem: The game crashes to desktop when I build a shack.
Cause: There may be several cause for crashing, but it's most likely due to maxed out memory.
Workaround: First double check using Skyrim Performance Monitor to make sure the cause of the crash is memory. If you're game is crashing when the game's memory reaches around 3GB, then the cause of CTD is memory overflow. If it is, you have have several options:

-Load your save and build your shack at a less crowded area.
-Uninstall some mods that use too much memory. (such as HD texture mods)
-Use texture compression tools such as DDSopt to compress your textures (so they'd use less memory)
-Use “ENBoost” to increase the memory the game can use.

The memory overflow is a general Skyrim flaw and doesn't have anything to do with this mod.