The current implementation defines the size fields as type String instead of type Integer. Further, the server side inserts a group separator in the strings.
This would be OK if there were some mechanism for the client and server sides to express the locale. Given the lack of locale specification, the two sides could have different settings and thus be expecting a "." group separator when a "," separator is used.
This problem is completely eliminated when the type is changed to Integer (or any numeric type).
An alternative solution is to stop creating the string content with a group separator.