When a listbox with value-list links to a fixed width field, the existing value is not not displayed in the form.
The attached database contains a table with a VARCHAR field (ITEMV) and a CHAR field (ITEMF). The Form ListTest contains two drop-down listboxes with specified value-lists. The ITEMV box works as expected. The ITEMF box does not display existing data, although it can insert or modify it.
When the listbox is governed by an sql statement, it works correctly
Unless there is a logic behind this, it looks like a bug.
EDIT: Now filed as bug 120640.
Ubuntu 18.04 LO 220.127.116.11