[bug] Keyboard focus lost on some components

OSX 10.11.6, FF 6.004 beta

Using the Surface Texture Engine as an example, do the following:

1) Edit the filter.
2) Zoom in on the Result area.
3) Choose the pointer tool and select the Brightness/Contrast 6.002 component.
4) Type Command-Z (undo). Nothing happens.
5) Select the Switch component. Type Command-Z. The "focus" is returned to the Result component.

I checked other components in this filter that did not respond to the undo command when selected. They are:

Brightness/Contrast 6.002
Blend
Hue/Saturation
Profile Gradient 6.002
Color Control
Offset
IntSlider control
Slider control

You probably need to check other components as well...