If the source has a space between the currency symbol and the number and the target does not (as in English), Studio shows a "Number is missing" error. In financial documents with lots of currency figures, this is tremendously annoying. My workaround: I use Ctrl+H to insert a space after every currency symbol, run a QA check, note any mismatching numbers, use Ctrl+Z to undo the space insertion, then manually correct the errors I noted.
It's been this way in Studio from the very beginning, unfortunately. This really needs to be fixed!