S5 + Cura issue: first layer on support fails

[frowin 2]

Hi,

 

we try to print a support with overhang which needs support. Unfortunately, Cura does not put support on the whole area but leaves an area with no support in the middle. I assume, that Cura wants to save support material and thinks, that the printer will use bridging. This works in 20% of the prints, in 80% not. The first layer which is placed on the support fails quite often. I attached some photos and some cura screenshots.

 

Is there a possibility to improve the slicer in a way, that it does not leave areas with no support? Or can one improve bridging?

 

We are using Ultimaker PLA material for print and Ultimaker PVA for support. Does this bridging fail because of bad adhesion of PLA on PVA?

 

As already mentioned, I attached photos, screenshots of slicing and of the support settings (basic settings from Cura)

 

Thanks in advance for your help and ideas :)