Some clarification on your problem, you're encountering 2 issues:

1. An accidental 'tap' is resulted sometimes when you're trying to stop a webpage that is scrolling
2. When you lift your thumb at your preferred/designated location on the web page, it continues to scroll slightly

Are these your problems?

1. Correct

2. The unintended click occurs seeming when take my thumb straight off after the scrolling has stopped. I have to quite deliberately stop the page scrolling completely to prevent a click occurring.

Hi Matt,

This isn't a setting with the Firefox app. The app just uses the input given to it by the OS (which gets its information from the hardware/screen).

So in this case you might look into adjusting one of the iOS settings related to tap vs. touch.

Go to Settings > General > Accessibility > Touch Accommodations > Ignore Repeat

Toggle this on (so you see the green) try increasing the amount to 0.15 Seconds

Scroll back up to the top and toggle on Touch Accommodations, then try using Firefox to see what the result it.

Also, if you're using any screen protector then you have a much higher chance of misread inputs/touches/taps. I let myself get roped into being my office's company phone fix-it person, and the most frequent issue was that the screen wasn't working (iOS and Android). Almost without fail it was due to the screen protectors, from the cheapest sheets of plastic to the $200 'sapphire' moldings, they all caused problems.

And not that this is extremely helpful right now, but sometimes the capacitive touch screen starts to fail and causes odd and seemingly random issues.