My MERGING+NADAC gives once in a while distortion/clipping at the highest (critical) peaks/transients close to full scale
You may have connected the MERGING+NADAC output (balanced) to an unbalanced input.
See here what is the difference between balanced and unbalanced.
Find here how to connect the symmetrical line out from the MERGING+NADAC to an unbalanced input
Never attempt to short pin 3 (or pin 2) to Ground on MERGING+NADAC DA's output, since the MERGING+NADAC Line Out driving circuitry is symmetrical but not floating.
Furthermore, as Unbalanced Inputs are traditionally more sensitive than Balanced Inputs, the - 6dB Analog level achieved by using only one of the MERGING+NADAC symmetrical outputs, will offer better signal level adaptation with less risks of overdriving the Unbalanced Inputs connected to the MERGING+NADAC.