You did not state what kind of welding was performed, but I will guess it was TIG. TIG uses a high voltage high frequency signal to initiate the arc. The high voltage leaks out of welding leads and that is probably what did the units in. Keep the welding leads at least 1 foot from the control cables. If the welding leads have to cross the control lines, make the crossing at right angles. Otherwise the usual items, minimize lead length, maximize distance between welding leads and suseptable cables, and if possible, have shielding (magnetic and electrostatic) between the welding leads and the victims.
Best protection would be to unplug the cables from the electronics before welding.