Dialog 4 stops during cycle, triangle characters on screen

I'm having an odd issue. I was pocketing with the Dialog 4 using G72*1 and G74*1, and at the end of the finishing cycle while rapiding away the machine stopped, the screen went blank for a few seconds then came back on with all the coordinates at 0.0. I switched to Mode 4 and back to Mode 9, and the screen looked normal again. I checked machine location and it kept the zeros I had set. Ran another part, it stopped again near the end of the program. I suspected it was heat related so I shut the machine down for the evening. This was after having it powered on for 5 days, the shop was about 80°, a temp gun showed 90° on the electrical cabinet and 99° at the hottest part of the operator console - over the monitor.

I left it off for 2 days, then tried it again. The machine was about 10° cooler. Ran 3 parts w/no issues.I left the control on overnight.

Next day, on the third part the screen suddenly showed triangles at each axis readout, but the machine kept running. 2 minutes later, the program completed correctly but the triangles stayed on the screen. Switched to mode 4 and back to 9, triangles disappeared. Ran another part, the machine stopped in cycle, the screen stayed on but the spindle stopped and servos stopped, as though the cycle stop button had been pressed. I had seen the Z axis coordinates changing to 0.0000 instead of correct negative Z location so I was afraid if I tried to restart it I might send the tool through the bottom of the part. So I stopped there for the evening and shut the machine off.

Yesterday afternoon I tried again. I'll post a video of what was happening on screen. Halfway through the G72*1 the triangles appeared and the Z readout kept changing to 0.0000 after each Z move. Later in the cycle the triangles disappeared and the readout returned to normal.
At no time did any error message appear on the screen.
I'm currently running the same program with no tool in the spindle to see what happens.

Has anyone here seen this happen on their machine? Any knowledge of what this means or how to correct this? What do the triangles mean?
I haven't tried reseating boards yet. This is a FP7NC, the major difference between this and a FP4NC is a 2 speed trans and variable speed spindle motor drive



Watch the Z axis. It's at 0.0000, it feeds up slightly to rapid to the center of the pocket, shows 0.0000, feeds down .250, then shows 0.0000 again.

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