Trouble parsing data

[flatmax]

I'm trying to populate json data which has shallow objects inside it - the maximum key depth is 2, for example :
{
key1:data1,

key2:{
key3:data3,
key4:data4
}

}

I'm getting a replace error - see below.

I am including in my webcomponent like so :

import { WebTable } from 'dable/web-table.min.js';

web-table.min.js:1 Uncaught (in promise) TypeError: t.replace is not a function
at web-table.min.js:1:2708
at Array.map ()
at web-table.min.js:1:2687
at Array.map ()
at WebTable.populate (web-table.min.js:1:2678)
at web-table.min.js:1:4512