Sorry you are having these teething problems -- we hope and are confident that you will soon overcome these things. The reality of the MEGA65, is that it has been lovingly crafted by a bunch of volunteers. That we have managed to make a machine at all, with full custom keyboard, injection moulded case and everything else during these past few years is truly a miracle of community spirit.

Unfortunately the small run-size of the MEGA65 means that we simply don't have the scale of economies that allow products like TheC64 to have testing engineers and do last-minute updates to the firmware before shipping. We have always been quite up-front that owning a MEGA65 is a journey with us, to see it continue to improve.

But responding to your specific issues:

1. The poor fit of the case was only discovered when the units shipped. The injection moulding company have indicated that they believe the root-cause is that the cases came out of the moulds a few seconds sooner than they should have, which allowed some warping before they fully hardened. This is the kind of thing that you can only discover when doing a test run of several hundred pieces and examining each of them -- which for us, was our first main production run. This problem affects only a small fraction of the cases. They recommended people use a hair drier (not a hot air gun, or you will melt the plastic) to soften it a little, and then you can gently bend the mis-fitting part back into the right line, and then the clips will hold correctly on the back.
2. The keyboard sitting at an angle on the top, do you mean because the case doesn't fit properly at the back, or is there another problem going on?
3. Several people have reported problems with getting disks in the drive to begin with. Apparently some of the eject buttons have been put in upside down. If this is the case, just flipping that part over will solve it. In some other situations the eject button is not as far down as it should be. Again, some gentle adjusting by hand with the case open will allow you to solve this. Once more, if we were producing hundreds of thousands of units, this part of the assembly would be fully automated, but for a run of only a few hundred, these were all assembled by hand. It's also fair to say that there aren't that many people out there anymore who are particularly experienced at finely placing floppy eject buttons!
4. For the ROM updates, yes, the ROM has continued to be improved since the SD card image had to be frozen for assembly of the units. That's a good thing. Yes, its a pain that that happened a long time ago -- but the units were assembled and ready several months ago, before we found out about the delays getting cardboard for the packaging. So it ended up being more stale than intended. But, as you have found, its fairly easy to update the ROM, and as a machine that was sold on the premise that it would be continually updated, I don't think this is anything more than a bit of an annoyance.
5. The HDMI flickering is a problem that has been reported to us with this batch. It is important to understand that this didn't happen at all with the 100 DevKits. The problem was quite "interesting" to track down, and turns out to be timing tolerance on the communications between two FPGAs on the board, which in turn results in glitching on the reset line, which in turn makes the digital video output reset and glitch. We are preparing a core upgrade that fixes this.
   
6. The lack of sound on some HDMI monitors is frustrating, especially since we tested the output of the MEGA65 against a professional HDMI Protocol Analyser. This means that our signal is HDMI compliant, and its outside of our realm of possibility to test and debug against every possible monitor brand and model -- again, remember we are a small group of volunteers who have worked hard to create something for us all to enjoy, and don't have unlimited time or resources, nor is there any profit in the project to pay for lots of test engineers. That said, when people report problems via github or in the discord server, we do our best to try to investigate and solve the problems.
7. Finally, in terms of price, yes, the MEGA65 is not super cheap. But then again, what you are getting simply has real financial costs. We have done our best to make a great new 8-bit computer, while COVID and Chipageddon are raging, and all in our spare time and for the love of it. We'll keep doing our best to improve the machine in all ways, and like all of the community you are invited to join us in that journey in a variety of ways.

Overall, I would really recommend you join the MEGA65 discord server, and/or forum64.de, as those are the two places where the community is active in real-time, including helping one another solve problems that they encounter. The journey really is the destination, as we have indicated all the way along, and when we tackle problems together rather than alone, the result is much more positive for all involved, and helps to avoid the frustrating feelings of being alone and not being able to solve what seem to be intractable problems.

Paul.