Tandem axle blow outs. Been there.
It's common for the the spring shackles to get over centered or jammed in the frame block. Usually when the front axle is lifted air born, the forward shackle can over center ending up underneath the rocker bar. When this happens the front axle is carrying 80% of the total weight.
Quick visual check, if all's well hit the rocker pivot with some PB blaster to make sure it's not binding.