I don’t remember seeing anything not invertible in the ODTs (the segmented splines should be as most of the transformations), however the RRT code definitely has some non invertible code, i.e. Red Modifier.
Edit: Actually, there is a clamp in for example transforms/ctl/odt/rgbMonitor/ODT.Academy.RGBmonitor_100nits_dim.ctl:
linearCV = clamp_f3( linearCV, 0., 1.);