KNX Integrators on Manufacturer Technical Support Quality

What has been your experience with KNX manufacturers' technical support? Share the good and bad. Hardware reliability is one thing, but the quality of technical support can make or break a project when you are stuck on-site with a device that refuses to behave. I want to hear about your experiences with manufacturer support lines. Which companies have experts who actually understand the ETS parameters and can help you troubleshoot complex bus behavior? On the flip side, which brands should be avoided because their support is non-existent or unhelpful? Whether it is a quick response to an email or a helpful technician on the phone, who are the heroes and villains of industry support?