Wrong result while extracting NDVI in Google Earth Engine

I have here a FeatureCollection containing some productive forests of the company I work for.

The age in month for each forest site is important to me, since my study only looks for forests that are between 1 and 5 month of age.

With this age I calculated, at a desktop GIS software, the maximum date and the minimum date to filter the Landsat 8 images inside a period of the year (September to May).

So, with all these informations together as a FeatureCollection in my Assets, I have to define a function to be mapped to the whole FeatureCollection containing company’s forests.

The function needs to get values from columns MIN_DATE and MAX_DATE to filter the Landsat images, apply cloud masking, calculate NDVI and return the feature to the collection with the mean of NDVI computed as a column.

I’ve already developed something here, but it keeps returning me some weird result.

The code:

/ Script to get historical NDVI for each productive area

// Import FeatureCollection 
var IPTalhoes = ee.FeatureCollection('users/ee_rootDir/toiFinal');

// Define function to map over collection 
function calcHistoricalNDVI(feature) {
  
  // Get initial and end date
  var dateIni = feature.get('MIN_DATE');
  var dateEnd = feature.get('MAX_DATE');
  
  // Import Landsat 8 ImageCollection
  var imgCollection = ee.ImageCollection("LANDSAT/LC08/C01/T1_TOA");
  
  // Filter imgCollection
  var imgFiltered = imgCollection
                    .filterDate(dateIni, dateEnd)
                    .filterBounds(feature)
                    .map(function updateCloudMask(image) {
                      var mask = ee.Algorithms.Landsat.simpleCloudScore(image);
                      var imgUpdated = image.updateMask(mask.select('cloud').lt(20));
                      return(imgUpdated);
                    });
                    
  // Calculate NDVI
  var imgNDVI = imgFiltered
                .map(function calcNDVI(image) {
                  return(image.expression(
                  '(b(4) - b(3)) / (b(4) + b(3))'
                  ).select(['B5'], ['NDVI']));
                });
  
  // NDVI mean inside a period 
  var NDVIMean = imgNDVI.mean();
  
  // Reducer statistics - mean by talhao
  var NDVIMean2 = NDVIMean.reduceRegion({
    reducer: ee.Reducer.mean(),
    geometry: feature.geometry(),
    scale: 30
    });
  
  // Turn dictionary with NDVI values to FeatureCollection
  var NDVIMean2Feat = feature.set('NDVI', NDVIMean2);
  
  // Return Feature as function result
  return(NDVIMean2Feat);
}

// Map main function over collection
var NDVITalhoes = IPTalhoes.map(calcHistoricalNDVI);

// Print results
print(NDVITalhoes);

The issue:

When I print the Feature Collection, what I see is that there is a column named ‘NDVI’ in FeatureCollection with an "Object" within, but when I open each feature in console, I can’t find any property with this name, and indeed there are only 27 properties while there are 29 columns for the whole FeatureCollection.

Can anyone help me out?

.filterBounds(feature.geometry())

var NDVIMean2Feat = feature.set(NDVIMean2);