For the atmospheric model
NRLMSISE-00 (src/main/java/org/orekit/models/earth/atmosphere/NRLMSISE00.java · develop · Orekit / Orekit · GitLab), a bug was corrected in the C version of this model in 2019: C version commit diff (2019)
It seems to me that the Orekit version has the same problem … but it needs investigation before opening an issue.
On the C source model page :
NRLMSISE-00 - Dr. Dominik Brodowski, the ftp site of the Fortran code (found in the Orekit java code) is no more available and must be replaced by http://uap-www.nrl.navy.mil/models_web/msis/msis_home.htm which is not reachable either … so I was not able to found the Fortran version.