[Lazarus] VirtualTreeView question, horizontal jump

[Jürgen Hestermann]

I am currently fighting with VirtualTreeView which I got running after having a hard time
with poor/non-existing documentation (which is a real pain for such sophisticated libraries).

But now I am stuck again:
I am able to create a tree (directory structure of a file system) but when moving down
with the keyboard the tree jumps horizontally out of view to the left each second move.
So at first I see my tree structure, on the next cursor down it is moved horizontally out of sight
and the next cursor down brings it back again (horizontally moved to the left) and so on.
I can scroll it back to the left with Ctrl+Left but it's a pain having to do this after each second cursor-down key.

I already inspected all properties but either they don't change anything (as "toExtendedFocus")
or they seem not to be related to this behaviour.

Has anybody an idea what can cause this and how it can be changed?