Growatt SPH5000 voltage question/issue

[bobbiecool]

Hi. I have a Growatt SPH5000 with 2 strings of over panels. The 1st string is 6 panels of 410w facing south and the 2nd string is 12 panels of 410w facing West. These panels are made by Eurener (see pic). The voltage of these panels are 28v, however under load they're 23.46v. The Growatt data sheet for this particular inverter states that it needs 150v per string to start producing energy, under load those 6 panels are 140v, obviously not enough to get it started. However, the inverter does start producing in the morning when the sun are on those panels, yet late afternoon the panel voltage tends to drop to nearly 120v (always from 120v -128v) when the sun is on the other string. The Growztt tech sheet states that 120v is the minimum requirement to keep producing power after it starts at 150v, this is where my problem is as sometimes the inverter switches off that particular string as its drops below 120v. My conclusion is the panels are undersized in voltage, that's certain. I'm also concerned that this could potentially lead to issues with the inverter as the voltage of the string can sometimes be outside of the working parameters of the inverter.
Am I correct in my assumption on this? I need to go back to the installer with all the info I can get