Unfortunately this is not the issue we are facing.
Reproducing the Issue
Post an FI document, also via BAPI / IDOC, Logistic Transaction, HR transaction or Custom Program and involve a TAX CODE with 2 or more Account Key active. Example: you want to post to a G/L account which is defined as an incoming G/L tax account (MWSKZ = '<' Input Tax category) but the tax code is defined as an output tax code (MWART = 'A').
We are using A1 which is output tax code and account 216100 allows output tax