Finally, you get to hear Sean and me again! Rob diagnosed his audio problems and ended up turning it off and turning it back on again. Naturally, that fixed it.
CI build should use VS2019, from @barnson, suggests that the WiX build should use the latest version of Visual Studio available to the build machine. Currently the continuous integration builds use Visual Studio 2017 and there are some useful features we could take advantage of if we upgrade. Being the noble sort, I volunteered to fix my own bug.
BUG: Light parses CDATA part in conditions wrong when >< is contained, from @quirrel1002, seems like a potentially odd bug in the .NET Framework XML parser. We took the bug to verify the bug is a problem in WiX v4, which uses .NET Core.