Msg Block hangs up

I am currently tracking data from a machine by messaging the data to a computer from several SLC 5/05 and Softlogix 5 computer. There is a one-shot in the rung to enable the msg. Every now and then, I will get the same data sent over and over hundreds of times. Could this be cause by a msg block hanging up? Any help would be greatly appreciated.

It could be the message block hanging up, or it could be the other PLC hanging up so the data in it isn't changing.

What exactly happens when a msg block hangs up? And what is the best way to prevent this?

Do you mean that the data arrives at the usual period but is always the same data, or that more messages than expected arrive ?

How do you tell one incoming message from another ?

All the machines have a SLC, when the process of the individual machine completes, it sends the data to the main server to store the process history. This is stored with serial number of the part. When the problem occurs the same serial number of the part is sent over and over hundreds of times, in the time span of just a few minutes. I have never caught it while it is in progress, and it always goes away on it's own.

We had on going grief with msg writes and finally went to just msg reads with no problems since.