Graham,

Thank you very much for your contribution. I did a let of small alterrations on the code and think that, with your support, I now solved the problem.
It could be formulated in a rule like: A curved feed-in should always be preceded by a small straight line more or less perpendicular to the line to feed-in on? G41/G42 must be active before the start of that "pre-feed-in".
If I stick to this rule all variations of the part program work correctly. Having the correct offset and no overshoot.
It's not so bad that the program requires this, if only it were specified somewhere.
Many thanks,

Wilfried