Pen Tool autocompleting mask on first click

[#1]

Hello, I've run into this a number of times and I haven't been able to narrow down the issue.

Essentially, I'm attempting to use the pen tool to add a mask to a layer from the composition window. On first click, the pen tool creates two vertices on top of each other and completes the mask. When I try to click on the next point I want my new vertex to exist at on the mask, I get the "pen tool add vertex" icon. This tips me off to the weirdly completed mask that was just created.

I am able to create masks inside the layer window, but for me, it is easier to just do them inside the comp window.

This is a consistent problem I've run into, but it doesn't happen on all of my projects, only randomly.

I am running Windows 10 and the latest version of AE (and have had this issue on previous AE installations too).

[#2]

If possible, make a video capture and upload the link to see better what is happening with your mask and pen tool. Your explanation is clear, but a picture is worth a thousand words.