Firefox for Android: how to tap 'go to last post'?

I keep having this problem: I like to tap go to last post and hold then I choose open in a new window. Most of the time the little last post image get selected, or it just takes me to the last post. Occasionally I can get it to open up the context menu. Maybe this has to do with the exact number of milliseconds that I am pressing? Anyway, it’s incredibly annoying and I would like it if there was a way to fix this.