How to clean up A/P discrepancies

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I recently inherited the accounting of a firm that did not have a lot of basic bookkeeping chops, so I've been doing a lot of cleanup work.  They are using Sage 100 Contractor 2019, which is completely new to me, so I have been learning on the go.  I've figured out most of what I need to know to this point, but today I ran into a problem that has me stumped. 

At 2 different points in the past, an employee wrote checks directly against A/P.  I found it because the A/P Aging report and the A/P balance on the Balance Sheet are considerably different.  I was able to track down the entries causing the problem, but I can't figure out how to correct them. 

When I try to enter adjusting entries, Sage tells me that I can't write an adjustment directly to A/P.  So I tried creating invoices for the necessary amounts, but marking their status Paid before saving.  Sage tells me that the transactions won't actually be written to the G/L.  Sure enough, after saving, the Balance Sheet A/P balance did not change.  So I can't figure out how to get the A/P balance corrected.  Any and all bright ideas are welcome!

Thanks so much!