Asking around in the PilotNET server's compcon homebrew channel, it's been suggested that the reason this happens sometimes and happens inconsistently is that it might be a case where some ID tag between Suldan and another lcp are getting confused and resulting in this error. Someone else who was encountering the same error installed Suldan on a blank comp/con account and no longer had this issue, so it might be one where several lcps are butting heads.
The other possibility being proposed is that if you have too many lcps installed, comp/con can sometimes "run out of space" when trying to load everything and this comes up as a missing/incompatible ID issue.