I have never been a fan of printers and less so multifunction printers. Recently, I've been wrestling with my fax because it stopped printing rx reports so I didn't know whether or not it was successful. Additionally, it was low on toner, and it was constantly flashing "Received To Memory". These problems are all related. It seems by default when the fax is low on toner, it won't print any reports or automatically print faxes. The solution is fairly simple.
If your machine is anything like mine, press menu, find "Fax Settings" -> OK -> Find "RX Settings" -> OK -> Find "Toner Supply Low" -> OK then choose "Keep Printing" and press "OK" again. If your problem is similar to mine, your printer should spring to life and output the missing reports and faxes. You will of course use up your toner more quickly.
I think this is a pretty annoying default.