In addition to our standard triage-and-q-and-a, today's meeting included a live demo of some of the work Rob has done (occasionally assisted by yours truly) in WiX v4. Take a look at the meeting recording! Rob promises more in future meetings as more and more of WiX v4 comes online.
Candle.exe should warn (instead of error) on duplicate preprocessor variables, from @barnson, is an excellent, well-thought-out request that WiX should match the behavior of its spiritual ancestor, the C/C++ compiler. We took the issue in WiX v4.0 and I volunteered to implement the change.
msi installer file created successfully but file has no owner and creating permission problems, from @paul-mateos, reports a problem that's specific to Docker. Sadly, we can't just say "Docker should fix itself" so we suggested a potential workaround and took the issue in WiX v4.x to possibly improve the behavior if we can get some Docker experts to help out (or become Docker experts ourselves).
Unable to launch Bundle (elevated) if access to 'WINDIR\Temp' folder is limited by SRP , from @Mefor, demonstrates a problem with the security mitigation introduced in WiX v3.11.1. While not itself a vulnerability, it prevents a bundle from executing when launched elevated with certain policies in place. Working around the policies is likely more churn that we want to introduce in WiX v3.14, so we took the issue in WiX v4.0 for further study.