Dude, I'm sorry to tell you, but at the start of each level, you just have to rush against a wall for the characters to assemble and become one.
But it's not very complicated to repair on Construct, I use this software myself and just apply the Solid behavior to the characters so that it can touch each other. But don't correct that before the votes are over jam, otherwise you risk deleting your project like I did.
Unless it is done on purpose, in this case sorry to have taken up so much space in your comment space (lol)