Well, in the second situation, fillippo disconnected two of the streets...I can't see what else he might have done.
In both of these cases, the routing server doesn't seem to have any other option besides to have you turn around on a dead-end. It's possible that the roads in question didn't have an end node, or had reverse connectivity and now that's fixed. There's nothing visibly wrong with either road, except the second one where that extra dead-end was disconnected. This is kind of a unique area where there's A LOT of dead-ends and very few loops. When you're heading the wrong direction, Waze wants you to be going the other way pretty quickly. When it can't find a way to go, it basically gives an error, but tries to recover from the error without crashing. The end result of this is routing onto a dead-end and bouncing back off the end. It won't give a turn-around instruction at the end. It's just going to give a "turn left onto..." and then the next instruction will be "turn right onto..." whatever road you started out on.
What it probably should do in these cases is make an announcement "Make a U-Turn where safe" and leave it up to the driver to find a place to turn around.