AC200MAX - PV Power drops from above 100W to below 10 W when

I rjust have bought an AC200MAX with 3 x 200 W PV panels from Bluetti and am testing it.
With a single panel I’ve reached up to 120W in ME Nov sun. After connecting panels with similar light condition in series (AC200MAX, black, red-black,red-black,red AC200MAX) the PV power reading dropped significantly to below . Each panel individually delivered a voltage exceeding 20 V. The total should be around 60 V - well below the 140 Vmax.
None of the cells was in the shadow. Do the modules have bypass diodes in order to mitigate the partial shadow effect?
Did I overlook anything in the manual or could my MPPT-charge controller a voltage issue?
Thank you very much for your advice

Best Regards