Alpha does not appear to work with NDI 5

[chiebert]

We use PPT-NDI to provide lower-thirds titles to OBS Studio streams. While trying to address another issue with OBS Studio, I updated from NDI 4.x to NDI 5.x (Core Suite/NDI Tools) and the OBS-NDI plugin to 4.13.0 (latest). After this change, all PPT slides' backgrounds are solid black (content still appears over the black). Since our lower-thirds NDI source is on top of the source stack, this obviously obscures the rest of the scene. NDI Studio viewing this source shows two strange coloured horizontal bars (orange and green) at the top of the feed. I could only get things back to normal by downgrading to NDI Tools 4.x (and OBS-NDI plugin to 4.10, since after that NDI 5 is required).

Is anyone else having this problem with transparency? And does it coincide with NDI 5 vs 4 use? Am I missing some other system dependency under NDI 5?

Running Windows 10 latest.