I’ve been able to reproduce this effect. It is to do with switching between mouse/ tablet and tablet pressure. The Deco Brush uses pressure in its strokes. If you use a mouse then ‘tablet pressure’ is set at 1 and all is well. If you use a tablet then pressure is from 0 -.99 and all is well. But there appears to be an issue when switching between the two (perhaps only with some tablets - I use a Wacom Intuos 2) when pressure for the mouse drops to zero and sticks there. What is interesting is that if you record a zscript with the Deco Brush in ‘no pressure’ mode then the strokes have no pressure info (so its not a display thing).
I’m afraid I can’t think of a work around apart from not switching between mouse and tablet during a session. It would be possible to write a script to edit the strokes to put in pressure but that wouldn’t be all that useful. Unfortunately there is no way of setting the tablet pressure using scripting.