Identify Sump Line Problem

What happens here

The video begins with the creator kneeling in a trench, explaining that a perfectly functional sump pump can still cause a flooded crawl space if its discharge line is clogged. He indicates a blockage somewhere in the existing pipe, which led him to cut the pipe. In the process of dealing with the blockage, an existing coupling in the pipe broke, necessitating a repair using new PVC pipe and fittings.

Goal: Understand the issue and the scope of the repair.