Large nested rollups can lead to elements being counted twice or more within a rollup.
The following process helps you to find, across all dimensions of your system, all rollups that contain elements consolidated more than once under the rollup.

The code isn't the cleanest and there are probably better methods to achieve the same result so don't hesitate to edit the page or comment.

It proceeds like this:

I came across hierarchies holding a single child.
While creating a consolidation over only 1 element might make sense in some hierarchies, some people just use consolidations as an alternative to aliases.
Either they just don't know they exist or they come from an age when TM1 did not have aliases yet.

The following process will help you identify all the "single child" elements in your system.
This effectively loops through all elements of all dimensions of your system, so this could be reused to carry out other checks.