Here's a development screenshot that Thomas shared with the team earlier today.
"The image shows the test solar system running with a user time step of 4 days.
Each object then subdivides this step into smaller intervals to remain accurate. The sun can advance 4 days at a time with no problem, but mercury needs to subdivide into 16 steps of 4 days/16 = 6 hours ..and so on.
The steps are power of two divided, so it is either 2 or 4 but not 3. The longer the user step, the more substeps each need to take." - Thomas
In short... moons thrown out the simulation because you turned up the time step too high? Soon to be a thing of the past.