Unity 3D: a simple model makes the lag on mobile

I checked Google or the Unity community but didn't answer my specific question.

Description of the problem

I am creating a simple Android game in Low Poly Style and I want to optimize it for that platform. All my models are made with Blender and are working fine.

I also created a simple house made from a cube with Blender, but when the player is near the house, the game lags! So I decided to do this cube house in Unity 3D to see if it lags behind:

Blue = player, Red and yellow = direction the player is facing

And surprise, the lag in the game too! And indeed. I do not know why. As you can see, this is a very basic house. When the player is in front of the door and can see the inner house (yellow arrow), there is a lag in the game, but when the player turns the camera to see another part of the environment (red arrow), there is no lag.

Attempt to resolve

• I've reduced the number of vertices, faces, and edges for all my Blender models, including my house, but this house is already lagging behind.
• I zoom out the side view of the camera player.
• I checked to disable occlusion but nothing to do.
• I've recreated a new Blender file for my home, but the problem is always there.
• I also exported my grid to .obj / .fbx but the lag is always here.

My question

What's up with Blender / Unity? What can I do?

EDIT

Here is a video of my problem. As you can see, when the player sees the house, he lags behind, but when the house is not displayed in the camera player, pfuit, no lag: Link

Profiler

Here is the profile when I play the game on a mobile device:

Red part → The player sees the environment, Yellow part → The player looks at the house. I see a 10-15% increase in "Graphics.PresentAndSync" on the browse screen when the player sees the house. I'll check it out in detail.