Application log: Display of logs:
In the display profile I_S_DISPLAY_PROFILE the field catalog for levelV1 (therefore levv1_fcat) was defined incorrectly.
For the entry with
REF_TABLE: &V2&
REF_FIELD: &V3&
the flag IS_TREECOL = 'X' was set. This flag indicates that this fieldshould appear in a separate column on the right in the navigation tree.
However, this is only allowed for fields in level 1.

Solution:
In the field catalog for this field set the flag IS_TREECOL to ' '(blank) or let it appear in level 1 of the navigation tree.