This is just guessing

Author: Brutus5000

src/main/java/com/faforever/api/clan/ClansController.java

@@ -11,6 +11,7 @@
 import io.swagger.annotations.ApiResponses;
 import lombok.RequiredArgsConstructor;
 import org.springframework.security.access.prepost.PreAuthorize;
+import org.springframework.transaction.annotation.Transactional;
 import org.springframework.web.bind.annotation.GetMapping;
 import org.springframework.web.bind.annotation.PostMapping;
 import org.springframework.web.bind.annotation.RequestMapping;
@@ -58,6 +59,7 @@ public MeResult me() {
   @PostMapping(path = "/create", produces = APPLICATION_JSON_VALUE)
   @PreAuthorize("hasRole('ROLE_USER')")
   @Deprecated // use POST /data/clans instead (with a founder in relationships)
+  @Transactional
   public Map<String, Serializable> createClan(@RequestParam(value = "name") String name,
                                               @RequestParam(value = "tag") String tag,
                                               @RequestParam(value = "description", required = false) String description) {