The attached test case demonstrates a situation where setting a property on one instance of a custom control can cause that change to leak to other instances.

See attached pictures for the two possible cases:

- failing case.png: overriding the spacing of the first custom control out of three fails, as it modifies the default spacing of the other two (from 20 to 0).
- working case.png: overriding the spacing of the second custom control out of three works, as the other two controls keep their spacing (20).

It can be reproduced with any JavaFX version starting in 14-ea+4 until latest 18-ea+7.

The issue can be related to this one JDK-8193445, as before it was applied the test case works, but after it was applied, the test case fails.