I'm seeing something sort of similar.
Details: Pre-PTO, two PW2, Solaredge SE3800H (no display).
This is what is happening:
1) Disconnect grid at TEG
2) Turn on inverter
3) Frequency at 59.6-59.7
4) Solar starts to be produced
5) Within seconds, frequency goes to 60.3-60.4
6) Inverter turns...