The gap between the supports at that point is smaller than the width of a train, so I guess they figured the minimal supports would be okay given that at those points the weight is distributed across 3 supports, but maybe the angle the front of the train hit that bank put like a fraction of a second more strain on the center support before it got re-distrubuted.

They need to add strain gages to all the supports on all the rollercoasters and check for other areas on this and other coasters that are experiencing more strain than expected.