re: Solar Panel service and troubleshooting.

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The panels are grouped in 8 groups of 6 before they go to the combiner, I thought that maybe they could be replace like that if I had a bad unit as they are also in series. So If one in the six goes down it affects the downstream panels. These are ten years old so they do not have the investors at each panel they are fed into an invertor. I have contacted a larger group about service but they have treated me like I have the plague , but things were different when I purchased a power wall, or if I need something new.

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So it matters how many MPPTs your inverter has or how many inverters you have. You cannot mix panels on a single MPPT. String inverters commonly have 2 MPPTs. This means you could have two different "groups" of panels. One group could be a different panel vs the 2nd group but all panels within a group must be the same.

You mention the "combiner." If this is just a DC combiner box then it sounds like your inverter has a single MPPT. If that is the case, all your panels must be the same or you risk oddball panels producing higher or lower voltage levels which creates a lot of problems.