Vertical wall layers not fused together with newer Cura versions

[jens 9]

Since some update my UM2 won't fuse wall layers (sideways layers) together. If I print vertical walls with more than one layer, those layers don't adhere to each other, like not at all. I can easily shove my finger nail in between without any resistance. It doesn't matter if I use external/internal walls or additional infill walls instead -- the result is the same. While that does lead to somewhat better (wall-)surface quality on a cosmetic level and less plastic gunk building up on the nozzle, the parts are way too weak.

I didn't have that when Cura was still in the 10+ version numbers. Of course, there would often accumulate a bit more of plastic gunk on the nozzle, but I could print thick-walled parts that would really have one single thick wall (and not several separate layers like a stack of leaf springs). With the new Cura, I didn't find any option to make wall layers fuse together. Would someone please point me in the right direction?

(Just in case: we're not talking about a mere underextrusion issue on the machine side of things. It's something with the slicing. I think it started somewhen with Cura jumping from 2-digit-dot-something to 1-digit-dot-something version numbers.)

Edited February 24, 2019 by jens