When loading a 4D pointset from a mps file (mitk pointset), the last timesteps are ignored if they do not contain points.
e.g.
Pointset A contains 5 timesteps:
ts 0: 3 points
ts 1: 0 points
ts 2: 5 points
ts 3: 6 points
ts 4: 0 points
When you load this pointset, the loaded PS will only have 4 timesteps!
example file attached