It could be a matter of individual taste, but I have recently switched from full dCS Vivaldi stack to Nagra HD DAC X and I am not looking back. I do use a transport in the current setup as well.
I would recommend sending an email to Krell's service department. I am confident that Patrick (or someone else there) will honestly try to help with the issue before they recommend to have the units sent to them.
In case anyone may have interest in adding transport to their Vivaldi stack, I just listed mine for sale (silver finish, mint, latest software). Feel free to contact me for details.
I have for sale my dCS Vivaldi Transport in silver finish and in mint condition, latest software version.
Asking price is USD 19.5k plus shipping or best reasonable offer.
Please contact me with any questions or to discuss pricing.
I have been thinking of trying Roon (with my Synology 713+) as well, but I had read (in the instructions) that Roon recommends NAS with 4GB of RAM, while my unit has just 1GB. Also, would need to add SSD...., so these requirements have slowed down the timing of my experiment a bit. Any...
I agree as well, the upsampler update to 2.0 Plus improved redbook playback by not a thin margin. It was a surprise to me. The update was very well worth the cost.