Training effect overestimated b/c heart rate zones disappeared??

The same problem with zones, but training effect working well. Somthing broken on garmin side.

I have the same problem, after cycling heart rate zone set to 0-1bpm. No problem with the training effect.

Anyone find a fix for this yet?

Still have the same issue on my side :(
However it affects only swimming and cycling activities, running activities are OK

Zones are set set right on the 935 itself.

There is your problem (well not YOUR problem, but just shows how Garmin's infrastructure is inept); Setting anything on the WATCH first is a no-no, you have to set these things on the website first and then sync those directly to the watch. This should take precedence in regards to ALL settings, which SHOULD filter down to everything else connected to garmin.

Order of precedence: Garmin Connect website>>>Garmin Connect Mobile (either android or apple)>>>Watch and subsequent devices.

In practice that should fix the issue, but, it's never that easy. I have seen, in real time, those HR zones after being manually set to what I need (All the zones not just one) just....change to some obtuse numbering after just setting them. Like I corrected the zones across the board on the website to suit my needs (fixing RHR, setting my Max HR, correlating my HR Zones etc...) and went and synced those to the watch, only to find after a refresh of the screen completely different settings there. And these weren't the prior numbers, like the site just simply didn't save my changes; these were ALL different (RHR is wrong, Max HR is really wrong, all the zones are wrong). Either the website is sentient and is making decisions or someone at garmin is in real time messing with me and screwing with my data. And this hasn't happened just once; i've had this happen across multiple devices. Not only that, even when there is no change and everything supposedly worked, the zones on the watch STILL don't match the website..or app (more on that below)

With the current 935 that I use, I couldn't even access all the HR zones on the app until I started beta testing the new features (all that showed up was the secondary zones). There is and has been a nasty disconnect within Garmin's syncing forever. Back when I had my 1st 235 I thought it was something isolated to that watch alone, but it's not the watch it's the shoddy programming across the platform and it doesn't look like garmin is ever going to be able to fix it.

My advice to you is to set the zones on the website, sync them to the watch via Garmin Express, disconnect the watch from GE, open the HR zones (one by one) and see if they match. If they do, great, but keep checking because it may just rubber band and go heywire. If they don't match, set each one to BPM and then set all the zones to default. That number should still look wrong, but if you use a different HR measurement (like LTHR for running) and set it back to that, it "SHOULD" correlate with your actual zones that you set on the website. I can tell you that for at least this watch it has realigned my HR zones, with little rubber banding. The only time I have come across a disconnect or random numbers is after a beta or live software release.

I know it's a lot of "MacGyvering," but it's the only thing I have personally found that corrects HR zones going bonkers. Good Luck.