In latest version of Preform some internal supports are baly attached to the surface where tip of support is placed.
on this print
https://photos.app.goo.gl/hXfZHbhsjdEoDAJcA
I added here internal support
https://photos.app.goo.gl/v74PSpDjmK1KrQa59
which created this shape of the support
https://photos.app.goo.gl/8y59sbgKYRtmZi4D7