diff --git a/src/app/core/substance-form/substance-form.component.ts b/src/app/core/substance-form/substance-form.component.ts
index 7fe1795b1..0b4857342 100644
--- a/src/app/core/substance-form/substance-form.component.ts
+++ b/src/app/core/substance-form/substance-form.component.ts
@@ -1467,8 +1467,10 @@ export class SubstanceFormComponent implements OnInit, AfterViewInit, AfterViewC
     const json = this.substanceFormService.cleanSubstance();
     const time = new Date().getTime();
 
-    this.substanceFormService.regenUUID();
-    json.uuid = this.substanceFormService.cleanSubstance().uuid;
+    // Always generate a fresh UUID for the draft copy — do NOT mutate the live substance,
+    // otherwise the save logic will treat a new substance as an existing one (PUT vs POST).
+    // A new UUID on every save ensures no two drafts share the same UUID.
+    json.uuid = this.utilsService.newUUID();
 
     const uuid = json.uuid ? json.uuid : 'register';
     const type = json.substanceClass;
diff --git a/src/app/core/substance/substance.service.ts b/src/app/core/substance/substance.service.ts
index c0340a270..ebebbcbb2 100644
--- a/src/app/core/substance/substance.service.ts
+++ b/src/app/core/substance/substance.service.ts
@@ -887,7 +887,8 @@ export class SubstanceService extends BaseHttpService {
         delete (substance as any).$$tmpStructureId;
     }
 
-    const method = type === 'import' || !substance.uuid ? 'POST' : 'PUT';
+    // Use POST for new substances (no uuid OR no version), PUT for existing ones
+    const method = type === 'import' || !substance.uuid || !substance.version ? 'POST' : 'PUT';
     const options = { body: substance };
 
     const url = `${this.apiBaseUrl}substances?view=internal`;
@@ -915,10 +916,8 @@ export class SubstanceService extends BaseHttpService {
 
   saveSubstanceWithoutValidation(substance: SubstanceDetail, type?: string): Observable<SubstanceDetail> {
     const url = `${this.apiBaseUrl}substances/novalid?view=internal`;
-    let method = 'PUT';
-    if (type && type === 'import') {
-      method = 'POST';
-    }
+    // Use POST for imports or new substances (no uuid or no version)
+    let method = (type === 'import' || !substance.uuid || !substance.version) ? 'POST' : 'PUT';
     const options = {
       body: substance
     };