Debug output when editing DropDown Custom Fields with multiple languages

New Install with php 3.1 RC4 (English) and added the NL (latest) language package.

The Custom Field (Only Dropdown) has Error Issues

Please see also the discussion at:
https://www.phpbb.com/community/viewtopic.php?f=466&t=2264111
With pictures and test results.

Made a test with adding new test Custom Fields:

Results with English + Dutch language

And User (preference) = English Language (is the below Result)
And User (preference) = Dutch Language (is the below Result)

Booleans (Yes/No) - OK
Date - OK
Dopdown - Box - ERROR !!!
Google+ - OK
Numbers -OK
Single Text Field - OK
Textarea - OK
URL (link) - OK

Important: It only happens when you Edit a Field (after it has made and saved)

Step 1:
So, try to make a custom field, add the different languages in the [EN] and [NL] Option fields, and then Save it.
Step 2:
Try to change the fields at the [EN] and [NL] and SAVE it.
You will see, the fields have not been changed and also the Error again.