One product selected in Collection but Collection displays different products?

[amiable_beaver]

Hi there. I'm having a hard time grasping what the issue is with my Collections. I have 2 different Collections. One of them has 1 product (Stallster Pillow) assigned as follows:

The other Collection (Stallster Genesis) as 4 products assigned as follows:

Both Collections with different products assigned

Here are the details of the Stallster Pillow product showing that it is in the "Stallster Pillow" Collection

With all this information, when I click on "All products" which is linked to /collections it shoes both collections as expected. However, when I click into "Stallster Pillow" Collection is shows products that are specifically NOT assigned to that Collection. What am I missing?

Step 1.)

Step 2.)

Step 3.)

Thank you for your help.

Best,

Michael