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

Not sure about the tracks, but the climbed floors is not related to GPS. It works in-house as well, it uses barometer (and the feature is available only on devices with barometer) My son's old vivosmart 4 got crazy all of a sudden, and ever since (more than a year now) he's climbing 10s of floors every day according to Garmin, while there's no change in reality, and before it he did 3-5 floors a day.

I only have a couple notes here for possible help.

Cure all for many issues is the good ol' hard reset (upper left button for 35sec until blank) and then turn back on and sync watch.

My GPS has been great  - possibly one of the systems in use that helps with the trees and big building is down or acting up?  Have you maybe started running sooner after a gps green / locked notification?  Maybe give it a few more seconds or a minute to lock well.

Barometric altimeter sensor can get blocked/clogged/dirty... I always shower with my watch after workouts or swim with it as well, which both I think help keep it a bit clear.  Garmin has recommended a soak in water and rinse to some people as a fix.  Sensor is a hole just at bottom of base of watch back by strap iirc.  or slightly hidden by watch band.  Could help.

Strange, must be some kind of bug, with these buildings on one side the current tracks are as expected actually with mutipath "bouncing" off the buildings. L5 signals would possibly cancel that out like you saw on the old tracks. Maybe Dual-Band isn't getting activated for some reason.

You could try changing the GPS setup around to see if if changes anything. Could also be a hardware issue that developed...any "accidents" that could have damaged your watch/moved the antennas around ?

Anyway there's zero chance Garmin would be doing that on purpose ;-)

Yeah, my bet is that something is wrong with settings and it's using the more convsertavie GPS setting without multi band. I tried setting them to other values then bringing it back to "All Systems" but that didn't helped. As last resort l'll try factory reset but maybe first i'll wait for new SW version ( or try beta even) to see if that helps first and i don't want to make all setup from scratch again 

maybe try powering off/on or a 30sec reset restart between the settings changes.  might help.  just a shot :-)

I believe the 30sec rest also refreshes the GPS index completely... I could be wrong(?), seems like it takes longer to get GPS lock on first activity anyhow.

what is the GPS firmware in your watch? Menu - >System -> About and scroll down a few pages , 13.00? 

yes, try to push and hold the top left power button till restarting (it is 20-30secs apprx)

You dont need to make all setup from scratch after a full reset, there is an automatic backup function in your watch , so dont need to worry. 

www8.garmin.com/.../GUID-EE48B393-454D-4F32-B8B0-F598F2E8CB0A.html

But be careful: I don't think that IQ apps configurations (like watchfaces in my case) are backed up and restored.

"nobody's perfect!" yeah, i have screenshots in my mobile about all my screens (FR965 and Edge 840 also) :)

yeah i have GPS 13.00. I'm on latest v23.20 global version. I tried restarting already ( Actually watch crashed itself  recently ).