diff --git a/ChangeLog.md b/ChangeLog.md
index cf5dd62..394da76 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -8,6 +8,7 @@
 ## UNRELEASED
 
 * `project createbom` stores release relations (`CONTAINED`, `SIDE_BY_SIDE` etc.) as capycli:projectRelation
+* fix slowdown/crash in `project update` for large projects (#121) introduced in 2.7.0
 
 ## 2.7.0
 
diff --git a/capycli/project/create_project.py b/capycli/project/create_project.py
index 68a86a2..3641366 100644
--- a/capycli/project/create_project.py
+++ b/capycli/project/create_project.py
@@ -33,9 +33,9 @@ def __init__(self, onlyUpdateProject: bool = False) -> None:
         self.onlyUpdateProject = onlyUpdateProject
         self.project_mainline_state: str = ""
 
-    def bom_to_release_list(self, sbom: Bom) -> List[str]:
-        """Creates a list with linked releases"""
-        linkedReleases = []
+    def bom_to_release_list(self, sbom: Bom) -> Dict[str, Any]:
+        """Creates a list with linked releases from the SBOM."""
+        linkedReleases: Dict[str, Any] = {}
 
         for cx_comp in sbom.components:
             rid = CycloneDxSupport.get_property_value(cx_comp, CycloneDxSupport.CDX_PROP_SW360ID)
@@ -45,31 +45,17 @@ def bom_to_release_list(self, sbom: Bom) -> List[str]:
                     + ", " + str(cx_comp.version))
                 continue
 
-            linkedReleases.append(rid)
-
-        return linkedReleases
+            linkedReleases[rid] = {}
 
-    def get_release_project_mainline_states(self, project: Optional[Dict[str, Any]]) -> List[Dict[str, Any]]:
-        pms: List[Dict[str, Any]] = []
-        if not project:
-            return pms
+            mainlineState = CycloneDxSupport.get_property_value(cx_comp, CycloneDxSupport.CDX_PROP_PROJ_STATE)
+            if mainlineState:
+                linkedReleases[rid]["mainlineState"] = mainlineState
+            relation = CycloneDxSupport.get_property_value(cx_comp, CycloneDxSupport.CDX_PROP_PROJ_RELATION)
+            if relation:
+                # No typo. In project structure, it's "relation", while release update API uses "releaseRelation".
+                linkedReleases[rid]["releaseRelation"] = relation
 
-        if "linkedReleases" not in project:
-            return pms
-
-        for release in project["linkedReleases"]:  # NOT ["sw360:releases"]
-            pms_release = release.get("release", "")
-            if not pms_release:
-                continue
-            pms_state = release.get("mainlineState", "OPEN")
-            pms_relation = release.get("relation", "UNKNOWN")
-            pms_entry: Dict[str, Any] = {}
-            pms_entry["release"] = pms_release
-            pms_entry["mainlineState"] = pms_state
-            pms_entry["new_relation"] = pms_relation
-            pms.append(pms_entry)
-
-        return pms
+        return linkedReleases
 
     def update_project(self, project_id: str, project: Optional[Dict[str, Any]],
                        sbom: Bom, project_info: Dict[str, Any]) -> None:
@@ -79,7 +65,6 @@ def update_project(self, project_id: str, project: Optional[Dict[str, Any]],
             sys.exit(ResultCode.RESULT_ERROR_ACCESSING_SW360)
 
         data = self.bom_to_release_list(sbom)
-        pms = self.get_release_project_mainline_states(project)
 
         ignore_update_elements = ["name", "version"]
         # remove elements from list because they are handled separately
@@ -90,13 +75,17 @@ def update_project(self, project_id: str, project: Optional[Dict[str, Any]],
         try:
             print_text("  " + str(len(data)) + " releases in SBOM")
 
+            update_mode = self.onlyUpdateProject
             if project and "_embedded" in project and "sw360:releases" in project["_embedded"]:
                 print_text(
                     "  " + str(len(project["_embedded"]["sw360:releases"])) +
                     " releases in project before update")
+            else:
+                # Workaround for SW360 API bug: add releases will hang forever for empty projects
+                update_mode = False
 
             # note: type in sw360python, 1.4.0 is wrong - we are using the correct one!
-            result = self.client.update_project_releases(data, project_id, add=self.onlyUpdateProject)  # type: ignore
+            result = self.client.update_project_releases(data, project_id, add=update_mode)  # type: ignore
             if not result:
                 print_red("  Error updating project releases!")
             project = self.client.get_project(project_id)
@@ -114,20 +103,6 @@ def update_project(self, project_id: str, project: Optional[Dict[str, Any]],
                 if not result2:
                     print_red("  Error updating project!")
 
-            if pms and project:
-                print_text("  Restoring original project mainline states...")
-                for pms_entry in pms:
-                    update_release = False
-                    for r in project.get("linkedReleases", []):
-                        if r["release"] == pms_entry["release"]:
-                            update_release = True
-                            break
-
-                    if update_release:
-                        rid = self.client.get_id_from_href(pms_entry["release"])
-                        self.client.update_project_release_relationship(
-                            project_id, rid, pms_entry["mainlineState"], pms_entry["new_relation"], "")
-
         except SW360Error as swex:
             if swex.response is None:
                 print_red("  Unknown error: " + swex.message)