Greg,
Since there is no contactor for the third phase, they may be using a corner grounded delta. In that case, the heating element will see the full 400 V across it and the current will be approximately double of the calculated. That comes a bit closer to the measured values.
Even with a corner ground, I would imagine the voyages will be the same between the legs. By the readings, the heater lost the top contact likely to a ground fault between top contact ant first element and lost LS3 or bad connection on the jumper betwen LS1 and LS3. A compound problem
