collectionView Animates Color on Reload - swift

Question

Whenever collectionView reloads, firstColor and secondColor mixes for a moment then get back to how they should be. For some reason adding gradient caused that problem. without gradient and with only one color this problem does not occur.
Here is the video link to the problem. Video
extension PostSurveyViewController: UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
return self.surveyColors.count
}
func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
let cell = collectionView.dequeueReusableCell(withReuseIdentifier: SurveyColorCollectionViewCell.identifier, for: indexPath) as? SurveyColorCollectionViewCell
cell!.setup(surveyViewModel.surveyColors[indexPath.row])
return cell!
}
func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
collectionView.allowsMultipleSelection = false
for index in surveyViewModel.surveyColors.indices {
self.surveyViewModel.surveyColors[index].isSelected = false
}
self.surveyViewModel.surveyColors[indexPath.row].isSelected = true
self.collectionView.reloadData()
}
}
class SurveyColorCollectionViewCell: UICollectionViewCell {
#IBOutlet weak var bigSquare: UIView!
let gradientLayer: CAGradientLayer = CAGradientLayer()
static let identifier = String(describing: SurveyColorCollectionViewCell.self)
override func awakeFromNib() {
super.awakeFromNib()
}
func setupGradient(_ survey: SurveyModel) {
gradientLayer.frame = bigSquare.bounds
bigSquare.layer.insertSublayer(gradientLayer, at: 0)
let topColor: CGColor = survey.firstColor.cgColor
let bottomColor: CGColor = survey.secondColor.cgColor
gradientLayer.colors = [topColor, bottomColor]
gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)
gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)
bigSquare.clipsToBounds = true
}
func setup(_ survey: SurveyModel) {
bigSquare.layer.borderWidth = 1
bigSquare.layer.borderColor = UIColor.systemGray.cgColor
bigSquare.layer.cornerRadius = 8
self.setupGradient(survey)
}
class SurveyViewModel {
var surveyColors: [SurveyModel] = []
func getSurveys() {
surveyColors = [
SurveyModel(firstColor: UIColor.white, secondColor: UIColor.white, isSelected: true),
SurveyModel(firstColor: UIColor(red: 255/255, green: 138/255, blue: 0/255, alpha: 1), secondColor: UIColor(red: 159/255, green: 0/255, blue: 73/255, alpha: 1), isSelected: false),
SurveyModel(firstColor: UIColor(red: 19/255, green: 146/255, blue: 299/255, alpha: 1), secondColor: UIColor(red: 123/255, green: 0/255, blue: 139/255, alpha: 1), isSelected: false),
SurveyModel(firstColor: UIColor(red: 68/255, green: 204/255, blue: 98/255, alpha: 1), secondColor: UIColor(red: 0/255, green: 88/255, blue: 139/255, alpha: 1), isSelected: false)
]
}
}
struct SurveyModel {
let firstColor: UIColor
let secondColor: UIColor
var isSelected: Bool
}