diff --git a/backend/hermes/app/db/database.py b/backend/hermes/app/db/database.py
index 260eb13..c860b24 100644
--- a/backend/hermes/app/db/database.py
+++ b/backend/hermes/app/db/database.py
@@ -25,6 +25,7 @@ import app.models.customer
 import app.models.knowledge
 import app.models.audit
 import app.models.user
+import app.models.inventory
 import app.models.repair
 import app.models.repair_estimate
 import app.models.system_setting
diff --git a/backend/hermes/app/models/inventory.py b/backend/hermes/app/models/inventory.py
index 9428b9e..ecfdfc9 100644
--- a/backend/hermes/app/models/inventory.py
+++ b/backend/hermes/app/models/inventory.py
@@ -103,7 +103,11 @@ class InventoryStockMovement(Base):
     created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())
 
     item: Mapped[InventoryItem] = relationship(back_populates="movements")
-    actor = relationship("User", lazy="joined")
+    actor = relationship(
+        "User",
+        foreign_keys="InventoryStockMovement.actor_user_id",
+        lazy="joined",
+    )
 
     @property
     def actor_username(self) -> str:
diff --git a/backend/hermes/app/models/repair.py b/backend/hermes/app/models/repair.py
index 53ba9e2..6b32497 100644
--- a/backend/hermes/app/models/repair.py
+++ b/backend/hermes/app/models/repair.py
@@ -56,7 +56,11 @@ class RepairStatusHistory(Base):
     created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())
 
     repair: Mapped[Repair] = relationship(back_populates="history")
-    actor = relationship("User", lazy="joined")
+    actor = relationship(
+        "User",
+        foreign_keys="RepairStatusHistory.actor_user_id",
+        lazy="joined",
+    )
 
     @property
     def actor_username(self) -> str:
@@ -105,7 +109,11 @@ class RepairDocument(Base):
     updated_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now())
 
     repair: Mapped[Repair] = relationship(back_populates="documents")
-    uploaded_by = relationship("User", lazy="joined")
+    uploaded_by = relationship(
+        "User",
+        foreign_keys="RepairDocument.uploaded_by_user_id",
+        lazy="joined",
+    )
 
     @property
     def uploaded_by_username(self) -> str:
diff --git a/backend/hermes/app/models/repair_estimate.py b/backend/hermes/app/models/repair_estimate.py
index b9d6a80..9cdda96 100644
--- a/backend/hermes/app/models/repair_estimate.py
+++ b/backend/hermes/app/models/repair_estimate.py
@@ -40,7 +40,16 @@ class RepairEstimate(Base):
     updated_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now())
 
     repair = relationship("Repair", lazy="joined")
-    created_by = relationship("User", lazy="joined")
+    created_by = relationship(
+        "User",
+        foreign_keys="RepairEstimate.created_by_user_id",
+        lazy="joined",
+    )
+    accounting_transferred_by = relationship(
+        "User",
+        foreign_keys="RepairEstimate.accounting_transferred_by_user_id",
+        lazy="joined",
+    )
     items: Mapped[list["RepairEstimateItem"]] = relationship(
         back_populates="estimate",
         cascade="all, delete-orphan",
@@ -92,4 +101,8 @@ class RepairEstimateEvent(Base):
     created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())
 
     estimate: Mapped[RepairEstimate] = relationship(back_populates="events")
-    actor = relationship("User", lazy="joined")
+    actor = relationship(
+        "User",
+        foreign_keys="RepairEstimateEvent.actor_user_id",
+        lazy="joined",
+    )