Only 3/4 of Anchor links Work

Site URL: https://www.taffguard.com/sizing-and-configurations/

On the linked page, I have four anchor links, which can be accessed with the buttons on the right side of the page.  I cannot convince the fourth, "Pocket Filter Configuration" to work.

I've tried copying the working links' code and just replacing the ID, I've tried entering the code manually, and I've tried variations on the code, and I get no results.

Something is off in the url of that last page in the index. I think this is a simple fix. I can copy the links for the other buttons and paste them in my address bar and get to the correct page, but not the last one it just goes back to the top where the buttons are located. 

That's my problem, no matter how many times I change it, and I copy-paste the exact same URL, it just won't work.