Gps very inaccurate suddenly

Note the two images are the same, just different scale showing the problem. 

Garmin-Sierra

Yes Garmin-Sierra I have. As I wrote the watch has been consistently accurate at gps. Just the last few runs have exhibited the kind of inaccuracy demonstrated in the screenshots. 

DB00, 

Okay thank you. I will send you an email so I can gather a few more pieces of information. 

Pray to the lord because could be your GPS Chip next to fail and turn off forever, this is the initial gps behavior before a catastrophic failure of Sony GPS Sensors used in FR945 watches, and there is not fix really.

You could restart your watch, update the CPE.BIN file, or use ANY official solution, but sometimes it´s just your GPS Sensor Chip; many FR945 users (me included) had reported this failure several times, but it´s a hardware problem, not software, so if your watch is still on warranty, return to garmin for a repair, after your warranty expires there is no solution than buy a new one.

Everything depends on the specific needs of your sport or activity, I personally use it for running and for MTB, in addition to the advanced metrics, however after this bad experience and even at the risk of leaving the Garmin Connect ecosystem, I decided to change brand.