Hi Ronan, thanks for your answer. For us the problem was that we run “normal” Matomo an Tag-Manager on one same site and included both codes. I reported it too in the german forum (Bestehende Tracking in Tag Manager verwenden ).
We haven’t integrated the tag manager anymore (which is a pity ;-)) but this is how the basic function of matomo works reliably again. We will now try to use the normal Matomo plugin with JS to implement the taging.
Do you have another idea?