Sketchup solid subtraction subtracts an unwanted piece of plane

I have no idea why this one fails to work. Attached a screen record.
I promise i selected two solids to do the subtraction, and after that, the resulting object is no longer a solid, when I look carefully, I saw there is an opening in an unrelated area, making the geometry not dense anymore:
Any suggestions? All comments appreciated!
SKETCH up subtracting unwanted plane (1).mov - Google Drive10-14 morning version.skp (757.2 KB)

i selected two solids to do the subtraction, and after that, the resulting object is no longer a solid, when I look carefully, I saw there is an opening in an unrelated area

I checked the file and the group instance called difference shows as a solid as well as the other object. Can you provide more description of the file and what was exactly done.
Did you try running the plugin Solid Inspector2 , very helpful for tracking solid issues.
Also, the objects are small , 3 13/16" square and sometimes SketchUp doesnt work well with small geometry. You could try the “Dave Method”, using components with a scaled up copy. It usually helps.
https://forums.sketchup.com/t/the-dave-method/49720

Using the native Solid Tools, I get the same flaw as appears in your animation. Fortunately, it is quite easy to repair: Open the difference group for edit and hide the top face (turn off view hidden geometry). Then zoom in on the problem hole, draw an edge across to the little jog in the side, and soften the new edge. Unhide the top, close the group and check entity info - it will be solid.

Like the others, I suspect that the small size of the model is a factor, though I don’t understand why the hole appears away from the part that is being subtracted. Perhaps the interactions between all the convoluted holes are confusing the Solid Tools subtract.

fix solid

that’s very help! Thanks!

now the issue is, although this time the void piece is easy fixed. sometimes it’s not obvious, is there any plugin that can help find such defects?

this time it seems the shape is perfect:
for forum.skp (585.6 KB)
here is a screen shot of what i did afterwards showing the bug again.

PS: i tried to scale up the volume to 1686438063381 ft3 but issue persists, is it true i have to create the shape large for this to work (rather than working out the details and scale up later)

any hints? Really hit a wall here
larger size cube subtraction.skp (594.3 KB)
attached is the file right before subtraction, after that it becomes not a solid