pianoleo, I am not sure I input a hidden time signature at all.
As far as I remember, I input either the key change on the last quaver of the first bar, or I input a double bar line at that place.
Dorico did the rest by its own magic…
I will try to reproduce it.
This line in the score is the viola part - modulation from D-Major to G-Major 
in the first violin there is a quaver upbeat in the new key.
[edit]
I have removed the time signatures in that area and re-input that double barline, voila, everything looks and works fine! The movement is in 3/4
I wonder, if the weird time signatures had been interpreted by my xml import and not by myself…
