sofles

Hi there I have a problem with cura 2.7, when I try to scale an object it looses outside walls (see attachment) in this case when I scale it to 37% it has all walls but at 36% it looses outern walls. This isn't happening to all objects but is very annoying. I checked the same model in ideamaker and slic3r and it scale without any problem even to 20% but I prefer to using Cura. Thanks for any sugestions