Swap Hierarchical Labels BT_PCM_SYNC and BT_PCM_CLK
The WLAN sheet box's PCM hierarchical labels originally correctly corresponded to the top-level sheet's local labels, but they were changed on commit a961a248, specifically M2_PCM_CLK and M2_PCM_SYNC became BT_PCM_SYNC and BT_PCM_CLK respectively, while keeping the top-level sheet's local labels the same. Doing so caused what is now SAI5_TX_BCLK and SAI5_TX_SYNC to mistakenly become swapped. Unfortunately, this error was not caught during the review process, nor the prototype phase since the Bluetooth's audio interface wasn't tested.
Here is where the swap was accidentally made: a961a248 (scroll down to see the highlighted line 2767 in dvk-mx8m-bsb.sch).
Even though the top-level sheet's local labels were assigned/renamed to SAI5 on commit 1df2cd4d, the mistake was unfortunately not caught then.
With these two swapped, the Bluetooth's PCM audio interface likely won't work unless the M2_PCM_CLK and M2_PCM_SYNC traces are cut and swapped on the board.
RedPine mentioned that the I2S/PCM interface is not supported by their firmware which we are using, so this issue may not matter anyway.