Actually ReplayGain seems to be tricked by the heavy ultrasonic noise present in DSD files.
Thanks for the plugin. I respectfully ask for a way to save temp files to RAM. I wanted to ABX 44.1 and 88.2 files but the lag in loading the bigger file was always noticeable when switching track. I have the temp folder on SSD but apparently it's not fast enough (SATA 3).
The lag comes from the sample rate change. Until ABX component is changed to account for that you should resample the 44.1 kHz file to match the other one's sample rate.