Tax problem after upgrade to 6x-2.7

I upgraded a site from 6.x-2.4 to 6.x-2.7, without installing 6.x-2.5 or 6.x-2.6.
Now I have a strange problem: in the checkoutscreen the tax is twice given: on top -in cart contents-, a correct calculation, under payment method the calculation is wrong. If I continue to review order and all further screens, the invoice(-e-mail) and so on the calculation still is wrong.
My tax is calculated with module uc_vat. The tax% is 19%.
The correct calculation is: tax = 19% * subtotal
The wrong calculation is: tax = 19% * order total.
There are no shipping or other costs. The subtotal excl. VAT AND the order total stay the same, only the tax is changed.
See attachment.

I did some testing (all modules, except ubercart, unchanged during all tests). When I take a databasedump from before the update of ubercart, install version 6.x-2.4 or 6.x-2.6 and make an order, all goes ok. After updating to 6.x-2.7 all still will be calculated ok.

When I take the today's databasedump in my test system, with ubercart 2.6 or 2.7 I have the same problem. When I use version 2.4 all calculations are correct. But after upgrading to 2.6 or 2.7 the error appears again.

I don't dare to go back in production to version 2.4, because the database my be changed with all error-consequences.

Do you have a hint or solution?