[Nexus 5 Q&A, Help & Troubleshooting] FFU5y:
I am similarly having the problem of GPS dropouts, but I have noticed something specific when they happen and was wondering if anyone else could confirm (or disconfirm) what I am seeing.

First, I have observed the problem only since (1) upgrading to LP and (2) having my screen repaired by the official LG warranty repairer here in Australia. They happened at exactly the same time.

I have seen the problem on cm12, cm12.1, and factory image 5.1, LMY47I. I have seen the problem with baseband 2.0.50.2.25 and with 2...21. I have not yet tried reverting the modem version, and the device is out of the warranty period.

Symptoms: GPS will be working fine (using Google Maps) then my point will stop moving. It will sometimes jump forward in big leaps if I am in suburbia, and I am guessing that occurs when a wifi network is detected and Google infers my position from that. Without intervention, the GPS doesn't recover.

What I have observed: Using GPS Test (by Chart cross) I have noticed that whenever this dropout occurs, the list of satellites disappears, and it displays no satellites as being 'in view'. As satellites are detected by signal, they are re-added to the lost but that is a slow process. If I manually redownload the aGPS data then the satellites will all be shown again, and usually a GPS signal is rapidly obtained after that. However, once it has happened it seems to happen again frequently until the phone is rebooted.

Rebooting always seems to fix the problem temporarily.

My hypothesis: whether due to a hardware problem, a driver problem, or some software problem, the data on the satellite position etc. (which is normally obtained via aGPS) is being lost, and the phone is not automatically re-obtaining it. The loss of the data means position can't be calculated (because that relies on knowing the location or satellites) and so gets lost, and the data not being automatically reobtained means that the phone can't get another lock until all the sat positions are retrieved from the satellite transmissions or the aGPS data is manually retrieved (such as by using an app).

So, the long and the short of it is - when people have a GPS dropout do they, like me, see that the satellite position info is lost? In GPS Test, that shows up as having no sats in view, and the list of sats across the bottom of the signal strength delay being blank (i.e. no satellite numbers). In GPS Status & Toolbox, I think it appears as the number of satellites being 0/0 (i.e. zero of zero - thus none in view).

I have also looked at the logcats from when this occurs, and I have not been able to identify anything I would consider unusual. I see the following:

05-22 14:24:40.318 W/ActivityManager(751): Unable to start service Intent { cmp=com.google.android.gms/com.google.android.location.fused.NlpLocationReceiverService (has extras) } U=0: not found

But that seems to happen all the time.

I might (if I get a moment) write an app to record GPS stats such as position and #of sats in view, and post it here so we can look for correlations. Anyway, as I said, if anyone can check if they are seeing the same pattern that would be great.

One final comment: because I can only check the number of sats in view using GPS Test app or the like, there is the possibility that they causing that apparent loss of satellite visibility. However, I have the problem even when they are not installed so I think even if what I have identified is incorrect, there is still a real underlying problem. I also don't consider 'flash to an earlier radio' a real solution. This isn't a Frankenstein desktop PC I am running - if I am using official releases of the OS etc, it should work.

Cheers.