When is a solid less another solid not a solid?

[jalsina]

For the first time, I'm having trouble with solid operations. I have 2 solids. When I subtract one from the other, the result is not a solid. When viewed in X-ray mode, there are a lot of spurious hidden lines drawn inside. If I delete the spurious lines, sometimes I get a solid, but sometimes not. Very frustrating. Anyone experience this? Causes? Cures? Thx.

[Dave R]

You wouldn't want to share the file with us so we could see what's happening and perhaps have some hope of giving you some help?