Reverse AR Adjustment created with wrong activity and tax amount calculated

Hello

We have a case where the final user adjusted an invoice, but the incorrect activity was used to adjust the lines type. for example, the Original Invoice was for $1100.00 and then an activity with tax rate code source = invoice was used to adjust the tax and the line, the tax line was adjusted correctly (100.00), but the line was adjusted (900.00 line and 100.00 tax) and now we have difference in AR and GL and cant find the way to reverse the adjustment, because the system keeps recalculting the taxes.

Please help

Dani