Growatt spf 5000es 3 phase configuration voltage stability

Hello all,

I've got 3 units of Growatt spf 5000es in 3 phase configuration.

Once i turn on some heavy compliance (Electric Kettle - 2KW, AC- 2.5KW) i can hear that the UPS beeps for a second and then stops. it sounds like a voltage drop or something like that.

Any ideas for solution?

Thanks,

Arthur