Major GPS divergence

Hi

Yesterday I did 3 training session (3k run, 40k Ride finishing by 10k run)

Data were correct on the first leg. (I used my bike computer for the ride)

When analysing the data of the10k run, I noticed Major GPS trackig issues.

The run was consisiting of 10 times 1k loop and It seems that the GPS lost tracking at km8.3

Then around km9.3, I had a massive elevation gain of 6,800 m over a distance of closed to 3k in no time. 

I definitely did go to the location as recorded by the GPS from km9.3.

This is the first time it is happening. Any suggestion will be welcome.

Cheers

Franck