Hello I will help you with your question,
Did you turn the adjuster all the way in so it is as short as possible? When you do and you can slip the drum on turn the adjuster back out until there is a slight drag as you put the drum on. It should be snug but not tight or loose.
The other thing to check is that the shoes are seated on the cylinder guides and the ebrake spreader. All the springs must be in place to pull the shoes together.
If this is the information you asked for please ACCEPT this answer. If not please ask