UMG Image with a UI material mask keeps rendering as a tiny square (32×32-ish) instead of filling my Overlay/SizeBox, even though the mask/material is correct.

Development Programming & Scripting
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Body (main post):
I’m rebuilding my settings UI as a right-side ScrollBox accordion in WB_Settings_Accordion and I’m stuck on a “Display Mode” row that needs a dark-green fill inside a custom hex-frame button.

Goal: IMG_DisplayModeFill should fill the entire button area and be clipped by a UI material mask so only the interior of the hex-frame is tinted.

Widget hierarchy (inside the row):

  • HB_DisplayModeRow

    • Left: TXT_DisplayModeLabel (slot = Fill)

    • Right: SB_DisplayModeCycle (SizeBox width/height override)

      • Child: Overlay

        • Child 0: IMG_DisplayModeFill (material fill layer)

        • Child 1: BTN_DisplayModeCycle (frame/button image)

        • Child 2: TXT_DisplayModeValue (text overlay)

What I did / verified:

  • The original button texture had tons of transparent padding, so I reimported a cropped version: uncropped_goodcopy_button.

  • I created a UI material M_ButtonFillMasked (Material Domain = User Interface). The material uses uncropped_goodcopy_button as a mask/alpha and outputs a solid FillColor where the interior should be.

  • The material preview/mask looks correct in the material editor.

  • On IMG_DisplayModeFill:

    • Brush is set to a Material Instance (MI_ButtonFillMasked)

    • Draw As = Image

    • Tint alpha = 1

    • ImageSize was previously 32×32, I set it to 0 (or cleared it)

    • Overlay slot alignment is Fill/Fill, padding 0

    • Render Transform reset (scale 1, translation 0)

Problem:
IMG_DisplayModeFill still appears as a small square (looks like it’s stuck around 32×32) instead of covering the SB_DisplayModeCycle area, even though the material mask itself is correct.

Question:
What in UMG commonly forces an Image widget (with a UI material brush) to render at a tiny fixed size like this? Is there a specific setting (Brush sizing, desired size, parent sizing, button style/overlay behavior, etc.) that would cause the image to ignore Fill alignment and the SizeBox size?

If it matters, the ScrollBox/accordion logic works fine; this is purely the fill layer sizing/rendering issue.