IR altimeter failure, drone climbs sharply and then comes down hard

Flying pixracer on a Tarot 650 frame with a TeraRanger Evo 60m for primary altitude control. I brought the drone up to about 7 meters and then sent it forward about 50 meters. At the end of that maneuver it started climbing and did not respond to throttle commands from the remote. It reached about 25 meters AGL and then began to descend. A few seconds after that I put it into land mode thinking that there might be a problem with the remote. It continued to accelerate down without slowing much at all and hit pretty hard, breaking one of the landing legs.

Logs show that the range finder distance dropped to zero when I pitched forward. I would have expected a time of flight sensor to max out distance if it lost sight of the ground though. Vertical position check bit and height to ground check bit both signal a problem but then a few seconds later return to normal even though the range finder never recovers. Hoping someone can shed some light on what exactly the drone thought it was doing and why.

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