diff --git a/docker-qgis/apply_deltas.py b/docker-qgis/apply_deltas.py
index 05b5947f3..00b6b5107 100755
--- a/docker-qgis/apply_deltas.py
+++ b/docker-qgis/apply_deltas.py
@@ -162,11 +162,19 @@ def __init__(
         self.descr = descr
 
 
+class FeatureNotFoundError(Exception):
+    ...
+
+
+class DoublicateFeatureError(Exception):
+    ...
+
+
 # /EXCEPTION DEFINITIONS
 
 
 BACKUP_SUFFIX = ".qfieldcloudbackup"
-delta_log = []
+DELTA_LOG = []
 
 
 def project_decorator(f):
@@ -254,7 +262,7 @@ def delta_apply(
     inverse: bool,
     overwrite_conflicts: bool,
 ):
-    del delta_log[:]
+    DELTA_LOG.clear()
 
     project = QgsProject.instance()
     logging.info(f'Loading project file "{project_filename}"...')
@@ -275,8 +283,8 @@ def delta_apply(
     if not all_applied:
         logger.info("Some deltas have not been applied")
 
-    delta_log_copy = [*delta_log]
-    del delta_log[:]
+    delta_log_copy = [*DELTA_LOG]
+    DELTA_LOG.clear()
 
     return delta_log_copy
 
@@ -288,7 +296,7 @@ def cmd_delta_apply(project: QgsProject, opts: DeltaOptions) -> bool:
     has_uncaught_errors = False
 
     try:
-        del delta_log[:]
+        del DELTA_LOG[:]
         deltas = load_delta_file(opts)
 
         if opts["transaction"]:
@@ -329,12 +337,12 @@ def cmd_delta_apply(project: QgsProject, opts: DeltaOptions) -> bool:
         )
     print("Delta log file contents:")
     print("========================")
-    print(json.dumps(delta_log, indent=2, sort_keys=True, default=str))
+    print(json.dumps(DELTA_LOG, indent=2, sort_keys=True, default=str))
     print("========================")
 
     if opts.get("delta_log"):
         with open(opts["delta_log"], "w") as f:
-            json.dump(delta_log, f, indent=2, sort_keys=True, default=str)
+            json.dump(DELTA_LOG, f, indent=2, sort_keys=True, default=str)
 
     return has_uncaught_errors
 
@@ -592,7 +600,7 @@ def committed_features_added_cb(layer_id, features):
                     f'The returned modified feature is invalid in "{layer_id}"'
                 )
 
-            delta_log.append(
+            DELTA_LOG.append(
                 {
                     "msg": "Successfully applied delta!",
                     "status": delta_status,
@@ -628,7 +636,7 @@ def committed_features_added_cb(layer_id, features):
                 logger.error(f'Failed to rollback layer "{layer_id}": {err}')
 
             has_applied_all_deltas = False
-            delta_log.append(
+            DELTA_LOG.append(
                 {
                     "msg": str(err),
                     "status": delta_status,
@@ -646,7 +654,7 @@ def committed_features_added_cb(layer_id, features):
             )
         except Exception as err:
             delta_status = DeltaStatus.UnknownError
-            delta_log.append(
+            DELTA_LOG.append(
                 {
                     "msg": str(err),
                     "status": delta_status,
@@ -1028,16 +1036,14 @@ def get_feature(
         QgsExpression.quotedValue(source_pk),
     )
 
-    feature = QgsFeature()
-    has_feature = False
-    for f in layer.getFeatures(expr):
-        if has_feature:
-            raise Exception("More than one feature match the feature select query")
-
-        feature = f
-        has_feature = True
-
-    return feature
+    features = list(layer.getFeatures(expr))
+    if not features:
+        raise FeatureNotFoundError(f"Could not find feature source_pk={source_pk}")
+    if len(features) < 1:
+        raise DoublicateFeatureError(
+            f"More than one feature match the feature select query source_pk={source_pk}"
+        )
+    return features[0]
 
 
 def create_feature(
@@ -1112,10 +1118,10 @@ def patch_feature(
     """
     new_feature_delta = delta["new"]
     old_feature_delta = delta["old"]
-    old_feature = get_feature(layer, delta, client_pks)
-
-    if not old_feature.isValid():
-        raise DeltaException("Unable to find feature")
+    try:
+        old_feature = get_feature(layer, delta, client_pks)
+    except (FeatureNotFoundError, DoublicateFeatureError) as exc:
+        raise DeltaException("Could not get feature", method=delta["method"]) from exc
 
     conflicts = compare_feature(old_feature, old_feature_delta, True)
 
@@ -1198,10 +1204,10 @@ def delete_feature(
         DeltaException: whenever the feature cannot be deleted
     """
     old_feature_delta = delta["old"]
-    old_feature = get_feature(layer, delta, client_pks)
-
-    if not old_feature.isValid():
-        raise DeltaException("Unable to find feature")
+    try:
+        old_feature = get_feature(layer, delta, client_pks)
+    except (FeatureNotFoundError, DoublicateFeatureError) as exc:
+        raise DeltaException("Could not get feature", method=delta["method"]) from exc
 
     conflicts = compare_feature(old_feature, old_feature_delta)
 
@@ -1302,7 +1308,7 @@ def get_backup_path(path: Path) -> Path:
     Returns:
         Path -- suffixed path
     """
-    return Path(str(path) + BACKUP_SUFFIX)
+    return path.with_suffix(BACKUP_SUFFIX)
 
 
 def is_layer_file_based(layer: QgsMapLayer) -> bool: