Im using openlayers 6, on mounted I use map().getView().fit(extent) for some reason on every refresh the zoom level is higher. any tips how to fix this?

Before using .fit(extent) I have to transformExtent to change projection from 5514 to 3857

this.map().setView(new View({
  projection: 'EPSG:3857',
  center: fromLonLat([50.075710, 14.472606]),
  zoom: 10,
  enableRotation: false
}))
extent = transformExtent(extent, 'EPSG:5514', this.map().getView().getProjection().getCode())
this.map().getView().fit(extent)

before refresh:

after refresh:

my problem is with map.getview.fit here is my code and here are the returned values coordinates after view.fit are a bit different

  console.log(transformedExtent)
  this.map().getView().fit(transformedExtent, this.map().getSize())
  console.log(this.map().getView().calculateExtent(this.map().getSize()))

before fit:

1. -27186.072153485078
2. 6701982.491006854
3. -5136.804165771885
4. 6724373.669054876

after fit:

1. -27186.072153485078
2. 6701493.775314425
3. -5136.804165771886
4. 6724862.384747305