Etoys programming question, clear pen trails from a textfield.

I hope this is the correct list for etoys questions...

I have a car leaving a trail of dots as it moves in the x direction.

I create a horizontal textfield for a 'track' (using a textfield from
the supplies menu).

The car moves along the textfield track and leaves dots for it's trail.

MY QUESTION:
I use 'clear all pen trail' from the textfield's viewer menu, but the
blue dots do not clear

I can clear the trail using the menu from the textfield's halo, but I
cannot clear the trail using the 'clear pen trails' from the viewer
menu of the the textield.

If I draw the pen trail outside of the textfield, the pen trail clears
using the car's viewer menu for 'clear pen trails'.

My question again - how to I clear pen trails using the 'clear all pen
trails' from the Viewer for the Textfield?

THanks