Garmin FR 245 GPS (glonass, galileo) bad accuracy.

I have 945 but same GPS chip/software. So my tracks are off and sometimes poorly but sometimes great. My FR10 tracks are more consistently better. Now the instant pace on the 945 can be sketchy whereas on my FR10 it's solid and responds well to me speeding up or down. The thing is I have worn both together and the 945 shows wrong instant pace but still the lap times are within 1 second of each other and that was through south of Spain in a coastal town with lots of high rise apartments so the GPS tracks were innacurate on both watches. The distance and overall pace was the same on both watches. 

I would just like better tracks and instant pace as that instant pace is much needed on intervals off the track. With 945 it will say 2:57/km then after 500m say 3:20/km when I know I never slowed down. Never have that with FR10 so the 945 it's randomly innacurate sometimes I feel it is accurate when not much power is needed but when more power is needed the FR10 is more accurate as it doesn't have the power saving chip but I'm completely speculating and could be wrong.