fit GPS track ends but everything else recorded fine (including miles, pace, elevation) - help to fix?

All the data recorded correctly for this run except GPS track ends ~4 miles early. all HR, pace, elevation, etc continued to record just fine and it has the correct paces/miles. Can someone help me figure out why and/or fix the .fit file? I tried a couple things at fit file tools, but nothing looks like it's made for this case.