The plug-in to export the STL file works fine most of the time, but had issues in the beginning. To overcome these,
I always work in mm, since 3D slicers (CURA) work in that best.
In sketchup, I always select the portions of the model and export 'selected'.. even if I want to export the entire model
I always review the slicing model in CURA and review the layers before generating the gcode for the printer.
I have found, that sometimes, the STL file will be missing huge portions of the model when they are imported into CURA. This is a real pain, because redrawing in scketch can be time consuming, but is still better than wasting time and material on the printer. If it is wrong in cura, it will be wrong on the printer. I found this out once on the printer..... and went back to view he model in CURA and the problem was visible there, too.
I've been reviewing the fusion360, but that has a huge learning curve and wish sketchup and the plug-in were a little more reliable.
I don't see any issues with the actual print out when I've:
1) Imported an STL into sketchup
2) Modified the model in sketchup
3) Exported the changes as a new STL
4) Imported the new STL into CURA
5) Exported the STL to create the gcode.