Decimal places of tolerance in calculated question types deleted when entered with comma

Problem
If the tolerance (error) of an answer in any of the three calculated question types is entered using a comma as decimal separator (e.g. 1,25) decimal places are deleted when saving the question (e.g. 1,25 becomes 1). Saving of the question works fine so teachers don't know about the deleted decimal places. As a result of the deleted decimal places, answers that should be within the specified tolerance are marked as wrong.

Expected behavior
When the language of the course / chosen by the user is set to German I would expect that Moodle accepts comma as decimal separator also for tolerance in all 3 calculated question types.

If this is not possible I would expect that Moodle throws an error message when saving instead of just deleting decimal places.