I want to thank the people here for the extensive discussion about the MMU's blockage issues. Like many here, I made the mistake of thinking that my extensive experience printing with a single extruder (and some dual-head dual extrusion) would make the MMU work easy.
I think the most important thing for me was to do serious failure assessments and extensive printing until I 'got it'. In the end, the main key for me was playing with temperatures. Even though I use exclusively filaments.ca filament, almost every different colour has its own temp. I start with 205/198, and then go up and down as necessary depending on the blockage. Until now, I have tried about 10 colours, and I would dare say only a couple worked without modifying the temperature. up or down 2C.
How do I do my failure analysis?
I start at 205/198 and then go until failure. Once that happens, I take out the filament that failed and look at it. If it has a hair, then I reduce the temp. If not, then I increase the temp. Repeat until success, and then lock down that number for that filament in a filament profile.
Like you, I wish there were more information about this. I think barring this, my advice to Prusa Research is: Just call this an "advanced" user or "professional" upgrade or "beta" product. I WANT Prusa to keep working on this. I had a Prusa i1 and it was freaking hard. But the constant work and feedback and input gave us the mk3. We are in early days for multicolour printing. This is the Gestetner. I want PR to keep working on it. At the same time, I can see why users feel betrayed: Not many people expected to buy this thing and spend hundreds of hours learning multicolour printing.
Thank you to PR and to all of you for the community.
tarek : )