There are two bugs I'm addressing in the VMT (Material) exporter.
1) $phongfresnelranges is outputting incorrectly.
2) The texture paths in VMTs is starting with a forward slash [ / ] and should not. This bug crept into recent updates intended to simplify various backend WW functions.
Fixes to both are being rolled into the next update. until then, manually edit your VMT file to have the correct data.
Both items now fixed in latest WW.