IT probably cracked from vibration and arc'd repeatedly to make it appear burned.
I don't know if it could cause the amp to cut out but if it's the only rectifier for either rail, it could cause the amp to drive DC to the output which could cause some amps to shut down.
This amp has 2 MUR3040's side by side. (this is the old zr style dx amp)
No Dc on output when I checked before I took it apart.
The amp just didn't seem to have the power it had before.
I thought maybe the crossover card solder joints were the cause till I saw the burnt rectifier.
I seem to remember this being an issue with DX700, and replacing them with a hardier case style. It's been a number of years, so I can't be sure. If you are still having an power issue, I can dig up service notes and advice.
The part number that you gave is a TO-218 case. The photos I have for the DX700 show a TO-218 case (x2). The DX350 has a single TO-247 case rectifier but I can't see the part number.
I am not very good at the sizes, but it is as big the power supply fets.
I thought they were 247.
I am curious if a mur3040wt would work, digi-key has some.
The link you gave has them but 100$ min order is what it says.