I think I have hit it: check the interplay between Line14 and M4.
Since the lines run slowly and products have certain length, M4 needs to wait for the next product to arrive and this waiting time is added to its relatively long processing time of 51 seconds.
It is really simple: in station MA5 you load MUs of 1m length onto a conveyor that runs at 0.0175 m/s. So, the conveyors from there on roughly run 1 MU every 1[m]/0.0175[m/s]=57,14[s] (translating into 63 MUs/hour). Also check your carroussel on the right (it runs about 64 MUs/hour).
So: I suggest you first make sure that your MUs have the correct lengths and distances between then.
That should enough input from my side.