CustomMSIDialog sample belongs to the 'Native MSI UI' support, which was a research-only effort. After WiX team released by far superior support for EmbeddedUI model the "Native MSI UI" functionality has been deprecated and moved into WixSharp.Lab.dll assembly. Thus it may or may not work with the rest of the system. Meaning that it's unlikely for the module that has been effectively discontinued to get fixed. Unless of course the problem exist for other use-cases (samples).
You have two options now.
You have two options now.
- You can migrate your UI on EmbeddedUI. It is actually quite simple and intuitive and you will not be limited in your UI development as you do with Native MSI UI. The samples are available.
- You may analyse the produced wxs file, identify the offending XML element(s) and use project on-XML generated event to fix the problem. If you go this way and share your solution I may have a look at it and possibly integrate it with the project validation routine so it can be fixed automatically as part of the MSI build procedure.