I recently downloaded @retrorockets' Mercury space capsule add-on, because I thought it'd be interesting to combinre it with various configurations of fuel tanks and engines to see what happens. But whenever I try to put a fuel tank below the capsule, I get three tanks sticking out horizontally from the bottom of the Mercury spacecraft. In this case I think it may be related to the fact there are three retrorockets on the capsule, but I have a similar issue with attaching engines with just the default components. Usually, when it happens, the engine sticks out sideways near the bottom of the tank, like a gigantic RCS engine, but there's only one rather than three. I still can't complete the build tutorial because this always happens.
How do I prevent this?
You can also rotate the part to the correct orientation, moving it near where you want it, then selecting the top of the tank and it should automatically connect the top to the nearest capsule connection