[position_calc] Data masking does not work all the time

[lerwys]

Problem: It works on a 30-40% basis for the BPMs. If we reboot the board it works sometimes. This could be related to the receiving synchronizing trigger

[lerwys]

This had to do with not receiving the TbT synch trigger. Once this is ok, data masking works. An upgrade would be to decouple TbT sync from data masking, as the two modes should be orthogonal to each other