The brief explanation is that Nitter worked by creating “guest accounts”, which were a leftover from when you used to be able to use the Twitter mobile app without an account. After creation, these accounts lasted for a month. The time since the ability to create these accounts was removed is nearing (has reached?) a month

This stopped happening for me once I lowered the back gesture sensitivity all the way. It was a little tedious at first trying to grab the very edge of my screen, but I got used to it pretty quickly