loader 0 kb of 0 kb (NaN%)

Hi, we are currently receiving this loading screen of "0 Kb of 0 Kb (NaN%) -see attached screenshot. It did work at one time and showed actual numbers/percentages, but has stopped working and we cannot figure out why. We are using the dataSource type of 'json'. Also, we were using the first element metdata for mapping with the types and captions, but changed it to using the mapping option and it made no difference.
An example mapping looks like this:

{
	"tbl1232_id": {
		"type": "id",
		"caption": "Record Id"
	},
	"tbl1231_applicant_name": {
		"type": "string",
		"caption": "Applicants - Applicant Name"
	},
	"tbl1232_status": {
		"type": "string",
		"caption": "Status"
	},
	"tbl1232_total_request": {
		"type": "number",
		"caption": "Total Request"
	}
}

and example data looks like:

{
    "tbl1232_id": 1243,
    "tbl1231_applicant_name": "test",
    "tbl1232_status": "Open",
    "tbl1232_total_request": 188
}...

Any idea why the loader doesn't work properly anymore?
 
Also, if it helps, we are currently testing v2.8.3 until we can get our angular 2.8.10 build up.