When you add remarks using the App, it's saved. But when you supply some remarks using the web it's lost. It's like this for a while now, didn't anyone notice this?
Yes, that's exactly what I wrote. The data from the web interface propagates to the app only at the first change, but then the changes stay cached, and do not refresh, when you change it on the server through the web interface again. Change from the app propagates well to both sides.
I've had several occasions where the notes I wrote using the site we're lost on the activity. I'll try to add some specific notes to see what exactly happens before I -overwrite- blank notes from using the app on the same activity. Maybe, when updating the activity from the app where no notes are shown, the blank value overwrites the cached notes written using the site.
Maybe, when updating the activity from the app where no notes are shown, the blank value overwrites the cached notes written using the site.
Yes, I bet, it is that case.
I do not know how long the caching bug on the app is present, but it is most likely a relatively new issue. I saw just couple of complaints about it, here on the forum. I'd suggest contacting the Customer Support and asking to be added to the case, since only if there are numerous users on the case, there is some chance Garmin will fix it.