One possible reason can be due to reading all the messages at a time. If we read all the messages with readMessages(bag), then the MATLAB process is being killed by OS or kernel. This is because there will be large number of messages in bag file and each consuming large size. If the available space in memory (RAM) is less than that, then the MATLAB process will be killed.
As a workaround, you can read one message at a time which does not consume lot of memory and the MATLAB process is not killed. Something like the following:
pc = readMessages(msg,row);