My firefox screen seems to shrink randomly

[Android Central Question]

While im using firefox and possible other apps like youtube, my screen seems to shrink suddenly, and then theres a close all prompt sometimes. Im not sure if its because i am unconsciously tilting the tablet, or if my fingers scrolling make it shrink. Its very frustratiing. It sometimes quickly flips from full screen to small. How can i fix this?

 

[belodion]

What tablet?