Tax Rate Name and Tax Rate Code updated in background while tax rate & tax rate amount stay unchange

I have a PO matched Invoice and I update the defaulted tax rate (local high 21% 0% Recov) to a low value (local low 6% 0% Recov). When I go out of the Tax Summary Lines and save and then go back in the tax rate and amout remain 6% and the previous amount BUT the tax_rate_name and tax_rate_code are reset to the defaulted local high.... This causes issues afterwards in tax reporting. Also in th ZX_LINES_SUMMARY_V view the same situation appears.