By default, viewport animations play in real time, skipping frames where necessary.

You can turn this off by clicking Time Configuration in the time controls, and then turning off Real Time in the Playback group box of the Time Configuration dialog.

When Real Time is turned off, all frames are displayed during playback. The playback may appear slow, but you'll know that you're seeing every frame.

You can also speed viewport animation by minimizing your viewports to quarter size.