diff --git a/build-executor/main.sh b/build-executor/main.sh
index f516521e16d8b76014e306eef44901e81b434e10..8789650df0df58c9a3c1cea95e4cebc04424c486 100755
--- a/build-executor/main.sh
+++ b/build-executor/main.sh
@@ -132,8 +132,10 @@ function run_docker_wl(){
   execute docker run ${strace} --rm -v $CIENV_JOBDIR/results:/results -v $MAIN_HEPWLBUILDDIR:$MAIN_HEPWLBUILDDIR -w $MAIN_HEPWLBUILDDIR -v $CIENV_CVMFSVOLUME:/cvmfs:shared $theimage $HEPWL_BMKOPTS || fail "[run_docker_wl] docker run $theimage"
   date
   for acvmfs in `ls ${MAIN_CVMFSTRACESDIR} | sed -e 's@cvmfs-\([^\.]*\)\.cern\.ch.*@\1@'`; do
-    echo "[run_docker_wl] Flush cvmfs trace for $acvmfs"
-    cvmfs_talk -i ${acvmfs}.cern.ch tracebuffer flush # fix BMK-3 (see CVM-1682)
+    echo "[run_docker_wl] cvmfs flush trace for $acvmfs"
+    if ! cvmfs_talk -i ${acvmfs}.cern.ch tracebuffer flush; then  # fix BMK-3 (see CVM-1682)
+      fail "[run_docker_wl] cvmfs flush $acvmfs" # fix BMK-136 (flush was silently failing, leading to missing cvmfs files)
+    fi
   done
   echo "[run_docker_wl] finished at $(date)"
   return 0
@@ -178,7 +180,9 @@ EOF
     echo "[run_shrinkwrap] reponame $reponame"
     date
     echo "[run_shrinkwrap] python /usr/libexec/cvmfs/shrinkwrap/spec_builder.py --policy=exact ${MAIN_CVMFSTRACESDIR}/$acvmfs ${MAIN_CVMFSTRACESDIR}/$specname"
-    python /usr/libexec/cvmfs/shrinkwrap/spec_builder.py --policy=exact ${MAIN_CVMFSTRACESDIR}/$acvmfs ${MAIN_CVMFSTRACESDIR}/$specname
+    if ! python /usr/libexec/cvmfs/shrinkwrap/spec_builder.py --policy=exact ${MAIN_CVMFSTRACESDIR}/$acvmfs ${MAIN_CVMFSTRACESDIR}/$specname; then
+      fail "[run_shrinkwrap] spec_builder.py" # fix BMK-136 (spec_builder was silently failing, leading to missing cvmfs files)
+    fi
     date
     trimname=${reponame/.cern.ch}
     spec_var=HEPWL_EXTEND_${trimname^^}_SPEC