Sometimes that “Seems like you already have an active order” message does not appear, but the chat box is greyed out still. So there’s no way to reply. Even refreshing the page does not work always. So have to go to order history manually, find the active order and respond there.
Also, you can’t drag and drop links or other text from the inbox, yet you used to be able to do so before the messaging system was changed. There were some other annoying bugs with it as well, but I don’t remember them all.
Seems like they don’t test out their new systems very thoroughly before implementing them, or then the testing is only done on one supported browser (Chrome), which I don’t use.