Reading parallel vtm files yields changing blocks
At the bottom you will find a dataset consisting of two timesteps that have been written from a 4 core run with VTK 7.1. As you can see the vtm files contain 7 blocks. Note that in particular block 3 (name: local_gran_pgl) is once a and the other time a this is due to the fact that in one time step two procs write and in the other only one.
Loading this into ParaView generally works. However, if you use an ExtractBlock to get the "Particles" block and then switch to the next time-step you will see that not all particles are shown. Additionally, the checkbox in front of "Particles" in the ExtractBlock Properties window is empty. Selecting this checkbox and applying will show you the correct particle data.
So basically having blocks that are written on different numbers of processors in different timesteps makes vtm unusable in ParaView. If you have any further questions do not hesitate to ask.