I think I've found a bug on the Instinct Solar. I guess it's fairly easy to miss this, as it only happens when there is no CPE present, and there perhaps additionally has not been a GPS fix for many days, thus no almanach data.
I pressed the key to save a GPS point. Instead of the watch waiting for a fix, which should have taken many seconds up to minutes with no almanach data present, the watch immediately assumed it knew where I was. It didn't. N and E coordinates were displayed as '------', height as somewhere above 20.000 Meters (which is unfortunately not enough to make me an astronaut). But it would immediately have been possible so save this point.
When I went into 'hiking', the point was acquired in an orderly fashion over about a minute, and I could then save that correct point.
The same thing happened a day later, after travelling hundreds of kilometers by car. The watch immediately assumed it knew where I was. Again, it didn't. A regular 'hiking' fix took half a minute.
What is happening here, I guess, is that the GPS-data is falsely marked as 'healthy' / up to date. I can well imagine that this was missed in testing, as almost everyone uses the CPE data.