To me, this has more to do with how it was exported in Inventor than how it was imported into MATLAB.
Using your *.ipt file, I exported from Inventor (File > Export > CAD Format > stl) in High, Medium, and Low resolution. They appear to import fine. However, Brep looks pretty bad. I used Binary format and mm for units.
unzip('bottom.zip');
% High res -159 KB
model = createpde;
importGeometry(model,'bottomHigh.stl');
pdegplot(model,'FaceLabels','on','FaceAlpha',0.5)
% Medium res - 77 KB
figure
model = createpde;
importGeometry(model,'bottomMedium.stl');
pdegplot(model,'FaceLabels','on','FaceAlpha',0.5)
% Low res - 49 KB
figure
model = createpde;
importGeometry(model,'bottomLow.stl');
pdegplot(model,'FaceLabels','on','FaceAlpha',0.5)
% Brep - 18 KB
figure
model = createpde;
importGeometry(model,'bottomBrep.stl');
pdegplot(model,'FaceLabels','on','FaceAlpha',0.5)
