Thanks, but the problem isn't with the K-1 Tax Basis.
I see now that M-2, Line 3 "Net Income per Books," per the instructions, should be overriden and replaced with Taxable Income. I assume we are supposed to override the BOY capital such that it is Tax Basis. Then the M-2 will match the K-1s. From speaking with another CPA for a Big 4 Firm, he says M-2 doesn't need to match SCH L and no reconciliation is needed for 2020.