When using Xskills most molds have a reduced amount of metal needed to fill them (all of them except ingot). For any of theses mold the pouring is looping when it reach the maximum. It goes up until the maximum amount (<100), then it start again at 0. And since it's almost impossible to be precise when pouring, it's impossible to cast anything.
I suppose Smithing + tries to fill the mold until 100 but it can't so it loops.
2 others players have the same problem in the comment of Xskills, . I don't know which mod need an update to avoid this incompatibility.