I ended up finding a solution. Pluginval 1.0.3 running via GUI was the one that failed on a true float parameter (filter cutoff), but then I tried CLI and realised that Pluginval was up to 1.0.4, and that version was failing on some other float parameters that were actually functioning as binary switches. So I tried the solutions here: Pluginval can set an AudioParameterBools to odd values - #32 by dave96 and that resolved the issue on Pluginval 1.0.4. I still get issues with 1.0.3, but I’ll leave the investigation there since I have everything passing on the most stringent tests on the latest Pluginval.