Another day, another weird bug. . .
I was trying to find an old thread topic while we were slow at work, and while going through each page back and forth starting from Page 1 on my Forum Activity widget worked as intended, when I went to the last page and got to the fifth page tab, it kept opening my phone's keypad with the digits from the last five pages pre-entered. This error is thus preventing me from working my way backwards through page tabs starting with the last page first.
Currently testing to see if this extends to other areas of the site, and will try testing on desktop view on my mobile browser.
UPDATE: It does indeed persist on the desktop view of my browser, as well as on other pages. It seems that anywhere you can view five page tabs in succession with two-digit numbers, and you select the first one in the set, it will open the phone keyboard.
ADDITIONAL: I am using the Samsung Internet Browser on my device.