Update:
I am now able to figure out how to reproduce this bug. I exited out of Safari, opened up the app, and then the bug appeared. The reproduction instructions listed below is now outdated. Here is the video of it in action:
Original Post:
After a browsed the DevFourms, when I go back into the site, the site logs me out. One time, I tried to log back in, I got an error. I experienced this issue on an iPhone 8 Plus device running iOS 13 Developer Beta 4, and I am on the site using Safari. This could be an issue with the browser, or the website itself. To reproduce this bug, go to Safari, log on to the DevFourms, then either close the tab the site is on, and wait for a few moments, then go to the site, or wait for the tab to refresh itself. You must run iOS 13 Developer Beta 4 to reproduce this.