Uploading images from multiple upload buttons

You aren’t handling the unsynchonized functions well. Also you’re using the deprecated upload button API.
It should be something like:

function saveProperties(){
//..your code code...
 let toInsert = {
//the properties as you wrote
};
 $w("#uploadButton13").uploadFiles()
  .then(uploadedFiles => {
	toInsert.url = uploadedFiles[0].fileUrl;
	return wixData.insert("Properties", toInsert);
    })
.then(results => {
//code code...
})
}