I thought the bugfix suggested by frank.papenmeier worked (see the last entry in PsychoJS platform version 2020.1 - Memory Leak in Visual Stimulus Setters).
And the bugfix seems to be included in the visual-2020.2 code (Polygon & Rect inherit the _updateIfNeeded()-function with the bugfix in class ShapeStim) as well.
So I guess that specific issue should be fixed in 2020.2?
In the each frame tabs of my experiment, there are if conditionals to decide whether to continue the routine occasionally. Besides there is no code in the each frame tabs…