diff --git a/rpc/json/service_test.go b/rpc/json/service_test.go
index 4094632ed45..91c591e6e32 100644
--- a/rpc/json/service_test.go
+++ b/rpc/json/service_test.go
@@ -5,6 +5,7 @@ import (
 	"context"
 	"crypto/rand"
 	"encoding/json"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -70,7 +71,7 @@ func TestREST(t *testing.T) {
 		{"invalid/missing param", "/block", http.StatusOK, int(json2.E_INVALID_REQ), `missing param 'height'`},
 		{"valid/no params", "/abci_info", http.StatusOK, -1, `"last_block_height":"345"`},
 		// to keep test simple, allow returning application error in following case
-		{"valid/int param", "/block?height=321", http.StatusOK, int(json2.E_INTERNAL), `"key not found"`},
+		{"valid/int param", "/block?height=321", http.StatusOK, int(json2.E_INTERNAL), "failed to load hash from index"},
 		{"invalid/int param", "/block?height=foo", http.StatusOK, int(json2.E_PARSE), "failed to parse param 'height'"},
 		{"valid/bool int string params",
 			"/tx_search?" + txSearchParams.Encode(),
@@ -95,6 +96,7 @@ func TestREST(t *testing.T) {
 			assert.Equal(c.httpCode, resp.Code)
 			s := resp.Body.String()
 			assert.NotEmpty(s)
+			fmt.Print(s)
 			assert.Contains(s, c.bodyContains)
 			var jsonResp response
 			assert.NoError(json.Unmarshal([]byte(s), &jsonResp))
diff --git a/store/store.go b/store/store.go
index a8233c6236f..3db9f724012 100644
--- a/store/store.go
+++ b/store/store.go
@@ -59,12 +59,12 @@ func (s *DefaultStore) SaveBlock(block *types.Block, commit *types.Commit) error
 	hash := block.Header.Hash()
 	blockBlob, err := block.MarshalBinary()
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to marshal Block to binary: %w", err)
 	}
 
 	commitBlob, err := commit.MarshalBinary()
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to marshal Commit to binary: %w", err)
 	}
 
 	bb := s.db.NewBatch()
@@ -78,7 +78,7 @@ func (s *DefaultStore) SaveBlock(block *types.Block, commit *types.Commit) error
 	}
 
 	if err = bb.Commit(); err != nil {
-		return err
+		return fmt.Errorf("failed to commit transaction: %w", err)
 	}
 
 	return nil
@@ -91,7 +91,7 @@ func (s *DefaultStore) SaveBlock(block *types.Block, commit *types.Commit) error
 func (s *DefaultStore) LoadBlock(height uint64) (*types.Block, error) {
 	h, err := s.loadHashFromIndex(height)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to load hash from index: %w", err)
 	}
 	return s.LoadBlockByHash(h)
 }
@@ -115,7 +115,7 @@ func (s *DefaultStore) LoadBlockByHash(hash [32]byte) (*types.Block, error) {
 func (s *DefaultStore) SaveBlockResponses(height uint64, responses *tmstate.ABCIResponses) error {
 	data, err := responses.Marshal()
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to marshal response: %w", err)
 	}
 	return s.db.Set(getResponsesKey(height), data)
 }
@@ -124,18 +124,21 @@ func (s *DefaultStore) SaveBlockResponses(height uint64, responses *tmstate.ABCI
 func (s *DefaultStore) LoadBlockResponses(height uint64) (*tmstate.ABCIResponses, error) {
 	data, err := s.db.Get(getResponsesKey(height))
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to retrieve block results from height %v: %w", height, err)
 	}
 	var responses tmstate.ABCIResponses
 	err = responses.Unmarshal(data)
-	return &responses, err
+	if err != nil {
+		return &responses, fmt.Errorf("failed to unmarshal data: %w", err)
+	}
+	return &responses, nil
 }
 
 // LoadCommit returns commit for a block at given height, or error if it's not found in Store.
 func (s *DefaultStore) LoadCommit(height uint64) (*types.Commit, error) {
 	hash, err := s.loadHashFromIndex(height)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to load hash from index: %w", err)
 	}
 	return s.LoadCommitByHash(hash)
 }
@@ -144,11 +147,14 @@ func (s *DefaultStore) LoadCommit(height uint64) (*types.Commit, error) {
 func (s *DefaultStore) LoadCommitByHash(hash [32]byte) (*types.Commit, error) {
 	commitData, err := s.db.Get(getCommitKey(hash))
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to retrieve commit from hash %v: %w", hash, err)
 	}
 	commit := new(types.Commit)
 	err = commit.UnmarshalBinary(commitData)
-	return commit, err
+	if err != nil {
+		return nil, fmt.Errorf("failed to marshal Commit into object: %w", err)
+	}
+	return commit, nil
 }
 
 // UpdateState updates state saved in Store. Only one State is stored.
@@ -156,7 +162,7 @@ func (s *DefaultStore) LoadCommitByHash(hash [32]byte) (*types.Commit, error) {
 func (s *DefaultStore) UpdateState(state types.State) error {
 	pbState, err := state.ToProto()
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to marshal state to JSON: %w", err)
 	}
 	data, err := pbState.Marshal()
 	if err != nil {
@@ -169,12 +175,12 @@ func (s *DefaultStore) UpdateState(state types.State) error {
 func (s *DefaultStore) LoadState() (types.State, error) {
 	blob, err := s.db.Get(getStateKey())
 	if err != nil {
-		return types.State{}, err
+		return types.State{}, fmt.Errorf("failed to retrieve state: %w", err)
 	}
 	var pbState pb.State
 	err = pbState.Unmarshal(blob)
 	if err != nil {
-		return types.State{}, err
+		return types.State{}, fmt.Errorf("failed to unmarshal state from JSON: %w", err)
 	}
 
 	var state types.State
@@ -186,11 +192,11 @@ func (s *DefaultStore) LoadState() (types.State, error) {
 func (s *DefaultStore) SaveValidators(height uint64, validatorSet *tmtypes.ValidatorSet) error {
 	pbValSet, err := validatorSet.ToProto()
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to marshal ValidatorSet to protobuf: %w", err)
 	}
 	blob, err := pbValSet.Marshal()
 	if err != nil {
-		return err
+		return fmt.Errorf("failed to marshal ValidatorSet: %w", err)
 	}
 
 	return s.db.Set(getValidatorsKey(height), blob)
@@ -199,12 +205,12 @@ func (s *DefaultStore) SaveValidators(height uint64, validatorSet *tmtypes.Valid
 func (s *DefaultStore) LoadValidators(height uint64) (*tmtypes.ValidatorSet, error) {
 	blob, err := s.db.Get(getValidatorsKey(height))
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to load Validators for height %v: %w", height, err)
 	}
 	var pbValSet tmproto.ValidatorSet
 	err = pbValSet.Unmarshal(blob)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("failed to unmarshal to protobuf: %w", err)
 	}
 
 	return tmtypes.ValidatorSetFromProto(&pbValSet)
@@ -215,7 +221,7 @@ func (s *DefaultStore) loadHashFromIndex(height uint64) ([32]byte, error) {
 
 	var hash [32]byte
 	if err != nil {
-		return hash, err
+		return hash, fmt.Errorf("failed to load block hash for height %v: %w", height, err)
 	}
 	if len(blob) != len(hash) {
 		return hash, errors.New("invalid hash length")