Field selection lost on saving the record

Field selection lost on saving the record

In On Add/On Load I add the option "[none]" to a lookup picklist with the following code:

clear Introducing_Player;
Introducing_Player:ui.add("[none]");
colIP  =  frmPlayers_List  [(Name != "Dummy" && !Name.contains(":"))] sort by  Name ;
Introducing_Player:ui.add(colIP.Name.getall());
Introducing_Player.select("[none]");

This works fine. But when I save the record, the field Introducing_Player reverts back to "-Select-".

Saving other selections in the same field works.
There is no code that could cause this behavior in Validate or On Success or in On User Input of any other field.

I can't seem to figure it out myself. Any help is greatly appreciated.