Chained Down/Heavy Feeling in Dreams After Performing WILD

I've been getting a lot of close attempts with WILD in the past couple weeks. I'm usually able to get sleep paralysis and enter the dream without much of a problem.

However, the difficulty comes when I actually enter the dream. I always feel like my body is super heavy, or chained down. Doing something as simple as getting up or moving my arm is incredibly difficult. And if I try too hard, I just end up completely waking up.

Does anyone have any solutions, or know what is causing this problem?

And before you ask, yes, I do get about 5 - 6 hours before WBTB.