Ethernet port speed statistics

Frequently customers are complaining that PTP550 is changing port speed from 1000 to 100mbps, I was not able to find eny log which will state, why device decided to downgade the speed, it is obviouse that device had some problems, probably bit error rate got high or something different. It would be very nice if we could get statistics, if port speed iis changing, what is the reason for this.