I noticed that the slider value indicator path is sometimes being clipped by things around it, and that over a certain text scale (about 2.0), the text in the value indicator doesn't draw at all (but the path does). I bisected this on the framework and engine sides, and it appears that turning on libtxt caused both of these problems.

Framework at good engine: b9bd51c
Framework at bad engine: 5a58b36

Last good engine commit: e44cd55
First bad engine commit: e61bb9a