drcheck does not seem to analyze lossy files correctly

[flip2flop]

I've been testing drcheck with a huge catalog of music, and found that the DR results for lossless files (flac/wav) are pretty much identical to the original DR tools' (dr14_t.meter by Simone Riva and foobar2000 DR Meter plugin). HOWEVER, there are a lot of discrepancies when it comes to lossy files (opus, mp3, etc.).
drcheck results were different compared to the original DR tools' for about half of my music catalog. The DR difference was mostly 1-2 points, but I found a handful where the difference was 3 or even 4 points. Interestingly when I ran drcheck against lossless (flac) files converted from the aforementioned lossy files, the results of drcheck were then correct (in align with the original DR tools).

Here's one example of a file where the DR difference is 4 points (DR9 vs DR13):

Result from dr14_t.meter by Simone Riva for lossy file:

$ dr14_tmeter --file Sneaker_Pimps_-_Johnny.opus
DR      = 9
Peak dB = -0.00
Rms dB  = -11.44

Result from drcheck for same lossy file:

$ drcheck analyze Sneaker_Pimps_-_Johnny.opus --show-channels
DR     Peak           RMS            Duration  DR (L)   DR (R)   Track
--------------------------------------------------------------------------------
DR13   3.74 dBFS      -11.45 dBFS    4:13      DR13.11  DR12.82  01-Sneaker_Pimps_-_Johnny
--------------------------------------------------------------------------------

Convert lossy file to lossless with ffmpeg:

$ ffmpeg -i Sneaker_Pimps_-_Johnny.opus johnny.flac
Input #0, ogg, from 'Sneaker_Pimps_-_Johnny.opus':
  Stream #0:0: Audio: opus, 48000 Hz, stereo, fltp
Output #0, flac, to 'johnny.flac':
  Stream #0:0: Audio: flac, 48000 Hz, stereo, s32 (24 bit)

Result from drcheck for converted lossless file:

$ drcheck analyze johnny.flac --show-channels
DR     Peak           RMS            Duration  DR (L)   DR (R)   Track
--------------------------------------------------------------------------------
DR9    0.00 dBFS      -11.45 dBFS    4:13      DR9.50   DR9.39   01-johnny
--------------------------------------------------------------------------------

From all the above I'm assuming that there might be an issue with the lossy->wav conversion process in drcheck