Can't get GPS Lock on HTC M8
I have identified same problem with the stock firmware 4.4.4 even after a factory reset.  This seems to be an issue with the stock ROM.

Other info: I contacted HTC.  First I was told that my phone would be replaced, now I am told it is a known issue and they are working on it.  But I have found very few reports of this problem online.  I would think that it would be affecting a lot more people.