I have had this issue for quite some time now (maybe a month or so?) that I can't select text in this editbox that I'm writing in and overwriting the text. Once the text is selected and "blackened" pressing any key doesn't overwrite it, only deleting said text with backspace works. Also when I delete the text with backspace, the blinking position indicator (sorry I'm terrible with the terminology) isn't there where it should be.
I'm using Google Chrome on two different machines (Windows 10 desktop, and ChromeOS chromebook laptop). I just tested whether this happens on Microsoft Edge on my desktop and it works normally, no issues at all.