Sometimes if you have a single nodein an invetory slot, and you place it, you are able to place it twice...
then it is "there" but it cannot be used. (no inventory access, etc), It might dissapear eventually, and does not drop anything if dug.
This sounds like a local lag spike. Unfortunately, the lag is quite frustrating. Our server isn't terribly optimized, but rather map generation with the new version of mapgen_helper and subterrane is extremely laggy. I will probably have to sacrifice the latest dfcaverns update to rollback these mods to the previous version until this is fixed.
DFcaverns has been extrememly laggy regardless of the version. I would say that lag is better now than it has been in the past. IDK that its a good idea to roll-back the update, Unless you have evidence that dfcaverns would be less laggy that way
FaceDeer and I briefly discussed it, there is much more amount of generation lag as the previous update. See: