I have noticed that when trying to sychronise the watch the previous workouts still remain in the scheduled excersises and therefore there is a message saying that it's full and cannot add new excersises in the calendar of the watch
So far the excersises from previous days were deleted and the excersises of the following days were added. But this doesn't work anymore and also there is no way to delete the previous excersises from the watch in order to create space for the new excersises.
I am not sure but I think that this happened after the latest update