For oscillator simulation, you should add .option maxstep=<value>. SPICE simulation uses dynamic timestep, and we normally set a maxstep that is smaller at least one-tenth of the expected oscillating period, to make sure the simulation timestep is not overly aggressive. In addition, oscillator means there at least two possible states in the steady-state DC solution, and you might want to consider setting initial condition for a certain voltage node or device current to help the simulation be consistent.
Consider uploading your schematic and specifying which .tran statement gives you a different result. It is possible that what you are experiencing is not a bug, but a matter of simulation technique that is required to handle certain circuits. Using a SPICE program always relies on knowledge and experience.
There are many reasons. For example, Mike might be trying to fix a bug but it turned out to need more work, or he might be working on an unreleased feature, etc.