I also have an M10 tablet with OTA10.1 with an non functioning location service and intermitent GPS icon. As per BQ's request I'm attaching some (fragments of) logs.

1) "# ubuntu-location-serviced-cli --bus system --test" outputs text like this:

 length=27 context=0x3b9968
I0425 12:36:40.585892 14050 android_hardware_abstraction_layer.cpp:135] static void com::ubuntu::location::providers::gps::android::HardwareAbstractionLayer::on_nmea_update(int64_t, const char*, int, void*): timestamp=1461635998000 nmea=$GPRMC,235958.010,V,8960.0000,N,00000.0000,E,0.000,0.00,050180,,,N*4C
 length=71 context=0x3b9968
I0425 12:36:40.585973 14050 android_hardware_abstraction_layer.cpp:135] static void com::ubuntu::location::providers::gps::android::HardwareAbstractionLayer::on_nmea_update(int64_t, const char*, int, void*): timestamp=1461635998000 nmea=$GPVTG,0.00,T,,M,0.000,N,0.000,K,N*32
000,E,0.000,0.00,050180,,,N*4C
 length=39 context=0x3b9968

and exits with a segmentation fault at a random moment in time.

2) Syslog filtered by 'location':

Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395044] (0)[11591:ubuntu-location]ubuntu-location[11591]: unhandled level 3 translation fault (11) at 0x00000000, esr 0x83000007
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395064] (0)[11591:ubuntu-location]pgd = ffffffc0551c9000
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395100] (0)[11591:ubuntu-location][00000000] *pgd=000000009500f003, *pmd=0000000069405003, *pte=0000000000000000
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395157] (0)[11591:ubuntu-location]
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395180] (0)[11591:ubuntu-location]CPU: 0 PID: 11591 Comm: ubuntu-location Tainted: G        W    3.10.93+ #1
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395198] (0)[11591:ubuntu-location]task: ffffffc036b62a00 ti: ffffffc036b18000 task.ti: ffffffc036b18000
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395213] (0)[11591:ubuntu-location]PC is at 0x0
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395226] (0)[11591:ubuntu-location]LR is at 0x0
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395242] (0)[11591:ubuntu-location]pc : [<0000000000000000>] lr : [<0000000000000000>] pstate: 60070010
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395254] (0)[11591:ubuntu-location]sp : 0000000000000000
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395265] (0)[11591:ubuntu-location]x29: 0000000000000000 x28: 0000000000000000 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395286] (0)[11591:ubuntu-location]x27: 0000000000000000 x26: 0000000000000000 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395306] (0)[11591:ubuntu-location]x25: 0000000000000000 x24: 0000000000000000 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395325] (0)[11591:ubuntu-location]x23: 0000000000000000 x22: 0000000000000000 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395345] (0)[11591:ubuntu-location]x21: 0000000000000000 x20: 0000000000000000 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395364] (0)[11591:ubuntu-location]x19: 0000000000000000 x18: 0000000000000000 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395384] (0)[11591:ubuntu-location]x17: 0000000000000000 x16: 0000000000000000 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395404] (0)[11591:ubuntu-location]x15: 0000000000000000 x14: 00000000f4ff09d7 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395424] (0)[11591:ubuntu-location]x13: 00000000f4e5c5e8 x12: 00000000ffffffff 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395444] (0)[11591:ubuntu-location]x11: 00000000f4ffad60 x10: 00000000f4e5c820 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395464] (0)[11591:ubuntu-location]x9 : 00000000f4e5e0b3 x8 : 00000000f4e5c850 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395484] (0)[11591:ubuntu-location]x7 : 00000000f4ffb0d0 x6 : 0000000000000001 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395504] (0)[11591:ubuntu-location]x5 : 00000000f4ffb50c x4 : 00000000f4e5c820 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395524] (0)[11591:ubuntu-location]x3 : 000000000000000b x2 : 0000000000000000 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395543] (0)[11591:ubuntu-location]x1 : 0000000000000000 x0 : 00000000f4e5c87c 
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.395563] (0)[11591:ubuntu-location]
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.400572] (0)[1:init]init: ubuntu-location-service main process (11586) killed by SEGV signal
Apr 25 12:31:57 ubuntu-phablet kernel: [  405.400644] (0)[1:init]init: ubuntu-location-service main process ended, respawning

3) /var/log/upstart/ubuntu-location-service.log is a constant repetition of this:

Instantiating and configuring: gps::Provider
__bionic_open_tzdata_path: ANDROID_ROOT not set!
__bionic_open_tzdata_path: ANDROID_ROOT not set!
__bionic_open_tzdata_path: ANDROID_ROOT not set!
__bionic_open_tzdata_path: ANDROID_ROOT not set!
__bionic_open_tzdata_path: ANDROID_ROOT not set!
Instantiating and configuring: remote::Provider
	name -> com.ubuntu.espoo.Service.Provider
	path -> /com/ubuntu/espoo/Service/Provider

4) The screenshot is the syslog filtered by 'gps'. 


Hope this info is of any use.