Since Ive printed it countless times, the print above was an overseen duplicate plate print I sent. i never expected v5 to f*ck it up!!! so i sent it blindly.
The screencaps were just captured afterwards to illustrate the issue.
As i said, I never had problems printing this with v4 in the past. SAME EXACT PIECE. NO MESH ERRORS.
This is from a week ago : Ideamaker vs S3D V5.0.1. STL is flawless (manifold, zero errors according to our Materialise Magics software - same info is given by Ideamaker, Netfabb, Microsoft's various 3D tools and _even_ S3D_ can't find anything wrong withe the stl)
I've printed this STL 4 times now on Bambustudio, Superslicer and Ideamaker : they have zero issues with it.
S3D changes it into this impossible-to-print item.