[missaoui]

That helps, but we can do better. Is #0208 working perfectly? And then in #0209 you get the video quality issues? There's not much in #0209 that would account for image quality issues, apart from perhaps the new 4.14.18 kernel.

When does the crashing start, or is that not in fact an issue? I'm confused about what issue it is you need addressed - video playback issues, or crashing? Or both?

If both, when does the crashing start?

Many thanks for your patience with me. I spent today many hours installing many builds including 2 reboots after each installation.

I am facing both issues: as of build #0209 always the video playback issues and additionally crashes starting with build #0523. I installed build #0208 and I noted only the video play issue but no crash.
Also build #0522 was only showing the issue with video playback quality including interruptions and progress bar but no crash.

In nutshell the video playback issue is always there as of build #0209 and the crashing issue came on top as of build #0523.
 

The boot time error message 
AE_NOT_FOUND, While resolving a named reference package element - LNKC
 is harmless, and should have been fixed in 4.16.

The Spectre V2 message should also be harmless - are you getting that with 4.18.9 in #0924? I can't tell as the start of your dmesg is missing - can you repost a complete dmesg from #0924?

Yes, I am getting the Spectre V2 message with build #0924 (I recorded a short video from the boot process to see it this time).
I tried to get a complete dmesg from #0924 but it seems that the start is not captured:

http://ix.io/1nxc
http://ix.io/1nxh