Your best shot is creating an issue for Mendix and I hope they get this solved soon because more people will suffer from this.
This seems not an easy fix that work for all languages and combination of device and app language. There are some pain cases with copy past and thousand separators too.
This pain is solved by bank apps in a common way with 2 input, one for the whole number, one for the fraction.
yes, this is not just a mendix issue, but a global issue.
copy pasting any numbers into any spreadsheet will give you a headache.
so you have to copy paste it into texteditor, find and replace all (atleast that is how i'm doing it).
maybe you could do the conversion in mendix somehow?