I had reported this problem a while ago already and I honestly don't know why it ever was like this in the first place. The strain seems to be getting inflated by breaks in an activity. In the pictures you can see that in the workout tab the times in the zones are correct and it's correctly distinguished between moving and activity time. The moving time should be the only time that counts. When looking at the strain tab (Belastung), it added another hour to Z4, some more time in Z3 and more here and there. Now why would the app count the break time at all? Why does it add those break times to random zones? This really makes the strain score completely unusable.