No, it is not an anchor layout. We have a complex layout containing nested border layouts, basically.
In regards to the "should not set width" errors...
It looks like this line in finishAxis is having an issue; it is trying to subtract a number from NaN (this is triggered from layout.calculate(ownerContext), which calls calculate. See below - size is NaN
center['set' + axis.sizePropCap](size - center.getMarginInfo()[axis.sizeProp]);