Forum not letting me post if I have more than one tab open

I have noticed that the forum won’t let me reply to more than one thread at once.

I usually access the forum and then the page with the alerts for me. From there, I selected 'open in another tab' for those threads I am interested into. So I have several tabs open, each displaying a different post. If I write a reply, it won’t get posted until I close all the other tabs, which is quite annoying. Is this avoidable, at all?