diff --git a/CHANGELOG.md b/CHANGELOG.md
index fc58fbb151..c438cbe0a5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,17 @@ should change the heading of the (upcoming) version to include a major version b
 
 -->
 
+# 5.21.3
+
+## @rjsf/core
+
+- Updated `MultiSchemaField` to call the `onChange` handler after setting the new option, fixing [#3997](https://github.com/rjsf-team/react-jsonschema-form/issues/3977)
+
+## @rjsf/utils
+
+- Updated `mergeDefaultsWithFormData()` to not merge `undefined` when there is a proper default for it, fixing [#4322](https://github.com/rjsf-team/react-jsonschema-form/issues/4322) 
+- Updated `getClosestMatchingOption()` to improve the scoring of sub-property objects that are provided over ones that aren't, fixing [#3997](https://github.com/rjsf-team/react-jsonschema-form/issues/3977)
+
 # 5.21.2
 
 ## @rjsf/core
diff --git a/packages/core/src/components/fields/MultiSchemaField.tsx b/packages/core/src/components/fields/MultiSchemaField.tsx
index c58b080424..7808f3289c 100644
--- a/packages/core/src/components/fields/MultiSchemaField.tsx
+++ b/packages/core/src/components/fields/MultiSchemaField.tsx
@@ -128,9 +128,10 @@ class AnyOfField<T = any, S extends StrictRJSFSchema = RJSFSchema, F extends For
       // so that only the root objects themselves are created without adding undefined children properties
       newFormData = schemaUtils.getDefaultFormState(newOption, newFormData, 'excludeObjectChildren') as T;
     }
-    onChange(newFormData, undefined, this.getFieldId());
 
-    this.setState({ selectedOption: intOption });
+    this.setState({ selectedOption: intOption }, () => {
+      onChange(newFormData, undefined, this.getFieldId());
+    });
   };
 
   getFieldId() {
diff --git a/packages/utils/src/mergeDefaultsWithFormData.ts b/packages/utils/src/mergeDefaultsWithFormData.ts
index e4ace80eff..f6a4f47814 100644
--- a/packages/utils/src/mergeDefaultsWithFormData.ts
+++ b/packages/utils/src/mergeDefaultsWithFormData.ts
@@ -49,5 +49,5 @@ export default function mergeDefaultsWithFormData<T = any>(
       return acc;
     }, acc);
   }
-  return formData;
+  return formData === undefined ? defaults : formData;
 }
diff --git a/packages/utils/src/schema/getClosestMatchingOption.ts b/packages/utils/src/schema/getClosestMatchingOption.ts
index c81ce42c70..400ebab75e 100644
--- a/packages/utils/src/schema/getClosestMatchingOption.ts
+++ b/packages/utils/src/schema/getClosestMatchingOption.ts
@@ -51,7 +51,7 @@ export function calculateIndexScore<T = any, S extends StrictRJSFSchema = RJSFSc
   validator: ValidatorType<T, S, F>,
   rootSchema: S,
   schema?: S,
-  formData: any = {}
+  formData?: any
 ): number {
   let totalScore = 0;
   if (schema) {
@@ -83,7 +83,11 @@ export function calculateIndexScore<T = any, S extends StrictRJSFSchema = RJSFSc
             );
           }
           if (value.type === 'object') {
-            return score + calculateIndexScore<T, S, F>(validator, rootSchema, value as S, formValue || {});
+            if (isObject(formValue)) {
+              // If the structure is matching then give it a little boost in score
+              score += 1;
+            }
+            return score + calculateIndexScore<T, S, F>(validator, rootSchema, value as S, formValue);
           }
           if (value.type === guessType(formValue)) {
             // If the types match, then we bump the score by one
diff --git a/packages/utils/test/mergeDefaultsWithFormData.test.ts b/packages/utils/test/mergeDefaultsWithFormData.test.ts
index 919b94ef83..3410b0de78 100644
--- a/packages/utils/test/mergeDefaultsWithFormData.test.ts
+++ b/packages/utils/test/mergeDefaultsWithFormData.test.ts
@@ -17,6 +17,14 @@ describe('mergeDefaultsWithFormData()', () => {
     expect(mergeDefaultsWithFormData(undefined, [2])).toEqual([2]);
   });
 
+  it('should return default when formData is undefined', () => {
+    expect(mergeDefaultsWithFormData({}, undefined)).toEqual({});
+  });
+
+  it('should return undefined when formData is undefined', () => {
+    expect(mergeDefaultsWithFormData(undefined, undefined)).toBeUndefined();
+  });
+
   it('should merge two one-level deep objects', () => {
     expect(mergeDefaultsWithFormData({ a: 1 }, { b: 2 })).toEqual({
       a: 1,
diff --git a/packages/utils/test/schema/getClosestMatchingOptionTest.ts b/packages/utils/test/schema/getClosestMatchingOptionTest.ts
index 5809ea0875..da16f32573 100644
--- a/packages/utils/test/schema/getClosestMatchingOptionTest.ts
+++ b/packages/utils/test/schema/getClosestMatchingOptionTest.ts
@@ -49,7 +49,7 @@ export default function getClosestMatchingOptionTest(testValidator: TestValidato
       expect(calculateIndexScore(testValidator, oneOfSchema, firstOption, ONE_OF_SCHEMA_DATA)).toEqual(1);
     });
     it('returns 8 for second option in oneOf schema', () => {
-      expect(calculateIndexScore(testValidator, oneOfSchema, secondOption, ONE_OF_SCHEMA_DATA)).toEqual(8);
+      expect(calculateIndexScore(testValidator, oneOfSchema, secondOption, ONE_OF_SCHEMA_DATA)).toEqual(9);
     });
     it('returns 1 for a schema that has a type matching the formData type', () => {
       expect(calculateIndexScore(testValidator, oneOfSchema, { type: 'boolean' }, true)).toEqual(1);