So Garmin is also doing programmes obsolescence ? ( GPS lost accuracy )

I have my FR965 since exactly 2 years. I've been and stil lam very happy with it. However this month i started to see some weird things with my GPS tracks they far far less accurate like the where a year ago for example. I'm using ALL Systems + Multiband GPS setting for best accuracy always. 

This moth i have lots of GPS inaccurate GPS tracks like this :

Today

While usually i had very nice looking tracks like this : 

year ago

So is it a 23.20 software that got bugged few months ago ( I'm also getting  extreme high number of climbed floors since few months ). Or is my GPS starting to decay ?