@Egika I would like to get a warning that there are unsynched activities that will get compressed. But what I think happened is that the activity was compressed while still recording it, rather than as a result of me recording a second one. But getting a warning in either case would help me to decide. I have a phone with me on really long activities, which would be the only reasonable situation for the watch running out of memory like that.
Now, what I am interested in, is whether I have a chance to get the GPS details of the activity of the watch or whether I can confirm whether it is compressed and I should give up. I have an FKT that I need to prove and feel rather ignored by Suunto support.