I'm dealing with the issue above, earlier the inverter would behave normally after 9pm, however, today its even beeping at midnight. Spoke with my installer and he said to switch Power setting from VDE0126 to VDE4105 and that the later version is more suited for our(Pakistan) grid. Something to do with voltage and frequency range. Does anyone know of the actual voltage/hz numbers for 0126 and 4105?

VDE0126 describes the disconnection of device(s) from grid doesn't have much to do or state anything about actual frequency or voltage range. "The automatic disconnection device is used as a safety interface between the generator and the public low-voltage distribution net and serves as a substitute for a disconnecting switch accessible at all times by the distributing network operator. It prevents the unintentional supply of electrical energy from the generator into a subnetwork disconnected from the rest of the distribution grid (islanding)..."

VDE4105 "This VDE application guide compiles the technical requirements for the connection of generation and storage units to the low voltage network of a network operator. It provides guidance for planning and decision making both for network operators and installers. The operator also receives useful information for the operation of such installations. "

So, if all else fails, the Infini Plus (or minus) manual or seller should/would hopefully explain what they mean and see as a difference between the two VDE Standards specified.

I don't know Infini's at all, so can't really help.