I have been looking a little further into this GPS issue, and you look like you were possibly right in regards to LOS not connecting to GLONASS

Using the GPS Test app, on the Satellites bar graph showing S/N ratio (ie not the circular one showing satellite possitions), there are numbers under the graph in boxes; empty outline with a white number. When a satellite is used in attaining a fix, the boxes become filled in with black writing; as opposed to empty with white writing. Now, the numbers underneath identify each satellite. Numbers less than than 35 are GPS and ones greater than 35 are GLONASS.
I never get any satellite numbered greater than 35 highlighted

even when I get a fix using 10+ satellites and the ones > 35 have great S/N ratios. Which implies to me either that
1. the GLONASS satellites are not being used in the actual fix
2. the GLONASS satellites are used to get better info regarding the GPS satellites locations, or my location, and not used for the actual fix
3. the OS/hardware is using the GLONASS satellites to attain & hold a fix, but is NOT reporting it back to applications as being used, and hence GPS Test doesn't know the satellites are being used and reports as such.
4. or something totally different.
The thing that surprised me, is that the exact same thing was happening on a different device; a Nexus 5 running an official Nougat RR