I'm starting to lose track of this thread.
The ADI-2 Pro/DAC has been doing a damn good job since day 1 (and by that I mean the 1st ADI-2 Pro). And I had already all of these different devices here on a high end HiFi and I used different RME models (ADI-2 Pro, ADI-2 DAC, ADI-2 Pro FS R BE). Initially with the ADI-2 Por I compared the sound between ADI-2 Pro and an Accuphase internal DAC-40 module really thorougly. I could do so, because it is possible in this setup to quickly switch between the two different DACs. The setup: Accuphase E-600 Class A amp and B&W 803D3.
The ADI-2 * series of devices do simply an excellent job of performing a "transparent" (in the sense of non-coloring) high quality D/A conversion. Nothing more, nothing less. If it doesn't sound well, then you have IMHO another issue.
Do not expect too much from the different D/A filters, these are so fine nuances in the sound .. it still sounds well no matter which one you use. These are nuances. B/T and PEQ are there to shape the sound according to volume and personal taste.
Really audible sound differences between AK4490 or AK4493 are also extremely unlikely.
No matter whether in the studio corner or in front of the HiFi. I never needed more that to simply turn the device on and use it. And it's also not required to make something like a science out of it. One can simply use it and thats all. And as I am listening at my HiFi always at the same level, I even decided to simply boost Bass a little statically and thats all. One knob, +1, +2 or +3 and thats all. Gain stays at the same level. Volume I control with the remote of the Accu. Easy going and then nothing but joy.
If there is something wrong, then it is almost certainly not the device itself. Then you should rather investigate in the area of room acoustics or even consider that maybe the amplifier / speaker combination is not so ideal for a really transparent working device like the ADI-2 *. I would even not exclude that these are simply psychoacoustic effects. You should do A/B comparisons.
Did you try to perform a reset to be on the safe side, to be able to exclude that an important parameter has changed?
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub13