I have successfully upgraded from version 2.4.2 to version 2.4.3-p1 and I have a bug that my orders totals are always 0€. The basket view is fine and gives me the correct information, but the "Order Summary" is wrong. Also when I place an order the correct data is saved in the background.
It is a core installation without additional installed modules...
I think this happened due to some mistake in the product. You can try another product and check. If the same error occurs, then you are missing one of the modules of Magento 2.4.3.
Kindly check these both things. If still facing the same then we need to check your code.
Do let me know if you face the same issue.
Click KUDOS and accept as a solution.
I suggest you try it with another product. If it still fails, please clear cache browser and check again.
Yes, I had to deal with the similar problem last week. I also recommend that you test it with a different product. If the problem persists, remove your browser's cache and try again. It may work on occasion.
This is the default Magento issue. Please upgrade the patch file for this. After that, your issue will be solved.
If my answer is helpful full then please set the accept solution flag and kudos flag so other members can take the same reference.