Since (1.1?) there has been an option to place a ghost belt over another belt in a different direction. A yellow arrow is placed on the belt showing the new direction and waiting for a bot to put a belt on it to change direction of the belt.

This doesn't work with the mod, and I have to do it manually.

Not a big problem, just reporting.

Thanks for the report. There might be needed some special handling for upgrading belt-entities

Related: Accidentally shift-clicked a miner sideways on an existing miner and it places the miner on top.

I have a save where somehow, I did that a gazillion times and every miner in my inventory gets added on top of the miner.. more than 40 times, but no idea how many total it is, it's still going, which is more than enough to tell me something's up, lol.

That's weird. Don't know, whats going on, but I'll have a look.
Usually, the mod simulates, that the entity is placed by the character manually, which should include checks like collisions and so on.

I would say, that both issues are fixed now with 0.5.7

Seems to be fixed. New error now, though. I'll open a new ticket.