FVWM: Mouse binding prevents some buttons from working on FVWM 2.7.0

I've bound ctrl-mouse1 to Resize a window:

    Mouse 1 W C ResizeOrMove

    DestroyFunc ResizeOrMove
    AddToFunc ResizeOrMove
    + I Raise
    + M Resize Direction Automatic WarpToBorder
    + D Move

This does what I want, but now normal mouse1 clicks (no modifiers) on certain widgets in YouTube and other video players don't work. For example, clicking on the "pop-out" button (attached for reference) on a YouTube video just registers a click on the video itself (causing the video to pause), not on the pop-out button.

I see this on reddit's video player too - clicking on the volume bar (attached for reference) makes the click go straight through to the video, causing it to pause instead of adjust the volume.

I see this on both firefox and chrome, so I know this isn't a browser issue.

In fact, I can replicate the problem simply with:

    Mouse 1 W C Echo "Hello"

If I take that line out, clicks go to the right widgets in the video players.

I've tried:

    Mouse 1 W C Echo "Hello"
    Mouse 1 W A --

…and:

    Mouse 1 W A --
    Mouse 1 W C Echo "Hello"

…to no avail -- I can't get my mapping to work and still be able to click on video widgets.

I see from fvwm.1:

    "Note that Fvwm actually intercepts all events for a
    window-specific binding and (if the focused window doesn't match
    any of the bindings) sends a synthetic copy of the event to the
    window. This should be transparent to most applications"

I would expect either no clicks to pass through at all, or for the clicks to go to the right widgets. This weird middle-ground has me stumped.

Help?

Thanks,

Stephen