This has likely come up before but I could not find a search result for it:
I have a block made up of layers B and C. The block is then placed on parent layer A.
When it was correctly displaying, turning off layer B or C turned off the block geometry on those layers. Turning off parent layer A turned off the entire block. All OK.
However, the file recently went strange without even messing with the blocks. In shaded mode, if layer B or C is turned off, the shaded geometry turns off, but the wireframe stays on without being able to grab it.
Refresh shade did not work because I could not select blocks. ClearAllMeshes did not work either.