An I sure????? You say it is a diode. You post a photo where I can barely see diode sized components, much less any indication as to which component you are asking about. And you ask if I am sure? What do you think.
You say that the markings on it are "AX 5E G1". You also say that it does not seem to have any marking for polarity. And you say it shows conduction in both directions.
Did you remove the part from the board to determine all of the above. In my experience parts can have markings that are on all sides. And, a diode can not be accurately tested in the circuit with a multimeter because there are usually other conduction paths which can change the readings.
I have repaired circuit boards for over 45 years and virtually every diode that I ever saw DID have a polarity mark on it. How on earth would the original assembly worker know how to mount it if there was no mark? Frankly I do not even know that it is a diode. It could be a resistor or a coil or a capacitor or any of many other parts. You seem to think it is a diode so I gave you a good guess at a part that would probably work IF it is a diode. But sorry, no I am not sure and from what you provided, no one can be sure. I only provided a good guess and a part that would probably do no harm.
If you want better information, then I would suggest two things. First a close up photo of the area of the board where this component is. Second, take it off the board and look for any markings that may have been hidden while it was mounted. And, with your multimeter set to a scale that uses a DC bias Voltage of only 1.5 Volts AND with the part removed from the board, take the resistance/conductance readings again and tell us what you get.
Close up photos of the part from all sides would also be helpful.
the non-burned diodes on the fluke instrument are measured and not leaky in both ranges, which means they are bidirectional .... are you sure my friend i can replace with 1N4007?