I don't think this is unique to the 935. There were lots of reports of issues with the 920, too.
I have a 920. So far I have not had the issues YOU describe (0, 1600, 0, etc). However, I do get skewed altitude readings when I go from inside to outside quickly. I can see the "right shape", but it loos slanted. Like my whole run was on a hill instead of an out and back. I can see where the "normal" peaks are still. However, I find that if I've been outside for a while then the altitude curve looks about like the "corrected" curve, and I usually don't bother with the correction. I don't remember having this problem last year (same watch), but it has been consistent since the outside temps have been in excess of indoor temps (aka summer).
I assume this has something to do with a temperature correction factor that either isn't working right, or that the 920 doesn't have. I never really looked into the inner workings of the 920 altitude.
I get something similar with my 920, usually on morning runs. I have an out and back 5k that's a gradual 100' uphill to the turnaround, but often the 920 shows me as starting 200' higher than the actual elevation, going level or slightly downhill to the turnaround, and then about 200' downhill on the way back...
"I'm thinking of a number between 1 and 10, and I don't know why!"