diff --git a/src/core/packages/root/server-internal/src/bootstrap.ts b/src/core/packages/root/server-internal/src/bootstrap.ts
index 0e91f368dc448..6327db1a71fe5 100644
--- a/src/core/packages/root/server-internal/src/bootstrap.ts
+++ b/src/core/packages/root/server-internal/src/bootstrap.ts
@@ -129,17 +129,17 @@ export async function bootstrap({ configs, cliArgs, applyConfigOverrides }: Boot
   }
 }
 
-function onRootShutdown(reason?: any) {
-  if (reason !== undefined) {
-    if (reason.code !== MIGRATION_EXCEPTION_CODE) {
+function onRootShutdown(error?: any) {
+  if (error !== undefined) {
+    if (error.code !== MIGRATION_EXCEPTION_CODE) {
       // There is a chance that logger wasn't configured properly and error that
       // that forced root to shut down could go unnoticed. To prevent this we always
       // mirror such fatal errors in standard output with `console.error`.
       // eslint-disable-next-line no-console
-      console.error(`\n${chalk.white.bgRed(' FATAL ')} ${reason}\n`);
+      console.error(`\n${chalk.white.bgRed(' FATAL ')} ${error}\n`);
     }
 
-    process.exit(reason instanceof CriticalError ? reason.processExitCode : 1);
+    process.exit(error instanceof CriticalError ? error.processExitCode : 1);
   }
 
   process.exit(0);
diff --git a/src/core/packages/saved-objects/api-server-internal/src/lib/utils/decorate_es_error.ts b/src/core/packages/saved-objects/api-server-internal/src/lib/utils/decorate_es_error.ts
index 1e32faafbba9f..3b336fa774850 100644
--- a/src/core/packages/saved-objects/api-server-internal/src/lib/utils/decorate_es_error.ts
+++ b/src/core/packages/saved-objects/api-server-internal/src/lib/utils/decorate_es_error.ts
@@ -9,6 +9,7 @@
 
 import { get } from 'lodash';
 import { errors as esErrors } from '@elastic/elasticsearch';
+import type { ErrorCause } from '@elastic/elasticsearch/lib/api/types';
 import type { ElasticsearchErrorDetails } from '@kbn/es-errors';
 import { isSupportedEsServer } from '@kbn/core-elasticsearch-server-internal';
 import { SavedObjectsErrorHelpers } from '@kbn/core-saved-objects-server';
@@ -38,7 +39,10 @@ export function decorateEsError(error: EsErrors) {
     throw new Error('Expected an instance of Error');
   }
 
-  const { reason } = get(error, 'body.error', { reason: undefined }) as { reason?: string };
+  const { reason: esErrorReason } = get(error, 'body.error', {
+    reason: undefined,
+  }) as ErrorCause;
+  const reason = esErrorReason || undefined;
   if (
     error instanceof ConnectionError ||
     error instanceof NoLivingConnectionsError ||