Issues with Indicator Applet Complete on MATE

I know this theme is primarily designed for XFCE, but overall it works very well with MATE. However, I've noticed that when using Indicator Applet Complete rather than the legacy system tray panel applet, the theme exhibits semi-transparent borders on some of the dropdown menus (most noticeably on the date & time, bluetooth, and sound indicators.) The menus themselves also seem broken, they appear far too small and with scroll arrows/buttons that don't really work properly to display the rest of the menus.

This was noticed on a Debian Bullseye (testing) system, but should be present in any distro that offers the latest mate with the Ayatana indicator applets.