diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0e75ad6..16e8863 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Removed
 ### Added
 
+## [4.28.1] - 2024-04-03
+
+### Fixed
+
+- Move back to Open MPI 4 on SLES15 at NCCS
+  - Testing showed crashes at C360 and under various other circumstances
+
 ## [4.28.0] - 2024-04-02
 
 ### Changed
@@ -27,6 +34,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
     - pFlogger v1.14.0
   - NCO 5.2.2
   - Various other updates
+- Move to use Open MPI 5 by default on SLES15 at NCCS
 
 ### Fixed
 
diff --git a/g5_modules b/g5_modules
index 582981a..5a2a7e1 100755
--- a/g5_modules
+++ b/g5_modules
@@ -139,9 +139,9 @@ if ( $site == NCCS ) then
 
       set mod2 = comp/gcc/11.4.0
       set mod3 = comp/intel/2021.6.0
-      set mod4 = mpi/openmpi/5.0.2/intel-2021.6.0
+      set mod4 = mpi/openmpi/4.1.6/intel-2021.6.0-gcc-11.4.0
       set mod5 = python/GEOSpyD/Min23.5.2-0_py3.11
-      set basedir = /discover/swdev/gmao_SIteam/Baselibs/ESMA-Baselibs-7.23.0/x86_64-pc-linux-gnu/ifort_2021.6.0-openmpi_5.0.2-SLES15
+      set basedir = /discover/swdev/gmao_SIteam/Baselibs/ESMA-Baselibs-7.23.0/x86_64-pc-linux-gnu/ifort_2021.6.0-openmpi_4.1.6-SLES15
       set usemod1 = /discover/swdev/gmao_SIteam/modulefiles-SLES15
 
    endif