Can strings PV1 and PV2 connected in series in a SUN2000-5KTL inverter

I've upgraded the 11 solar modules connected in one string (PV1) from 330w to 450w and I'm experiencing two issues:

1) AC Output is limited to 4kW

I've reviewed the statiscal information of the old pannels and all the maximum peaks in the last two years are just 4000w, so I wonder is there any power limitation per string.

2) In partially cloudy conditions the inverter is suffering unexpected shutdowns with no alarms and apparently due to voltalge higher than 500v in the connected string.

This only happens with the new solar modules

The new solar modules have the following parameters:

Pmax     450w

Vmp     41V

Imp    10.98A

Voc    49.6V

Isc    11.53A

One possible solution I'm considering is to split in two strings (6+5) connected to PV1 & PV2, but someone suggested to interconnect  PV1 & PV2 putting them in serial, so I would like to know if this can be done??

In addition in FusionSolar String configuration mentions PV strings are connected in 2-in-1 mode or "2-in-1 string", does this refers to the previous mentiones configuration?

Thanks in advance,

Enrique