When running on the treadmill, my FR235 registers a slightly lower pace then what I'm actually running--that's to be expected away from GPS. However, either once I hit the 2.75 mile mark OR start running at a mph of 7.3 or higher, my watch stops tracking my pace and cadence. The faster I run, the slower my watch says I'm running. Here's a chart from a recent run:
You can see it's at a consistent pace until the 2.75-ish mile mark. I started running faster at that point, and suddenly my watch thought I was walking.
I only have this issue on the treadmill. I don't have the issue running on an indoor track.
I frequently run outdoors with the GPS enabled to in theory my watch should be calibrated.
I contacted tech support about the issue last week, and a technician gave me some steps to follow to fix the issue that involved deleting files off the watch. These steps fixed the issue for less than a week.
I've had the watch for a year and a half.