UIB payload issue

bug.json

{
	"message": {
		"receivers": [{
			"name": "name",
			"address": "917358445777",
			"Connector": "917358445777",
			"type": "individual"
		}],
		"parts": [{
			"id": "1",
			"contentType": "text/plain",
			"data": "[{\"type\":\"text\",\"text\":\"Transportation is\"}]",
			"size": 1000,
			"type": "body",
			"sort": 0
		}, {
			"id": "2",
			"contentType": "text/plain",
			"data": "{\"buttons\":[{\"id\":\"a^ea26ef70-1339-443d-b0eb-026dc00d54f0\",\"title\":\"To move and build a new home\"},{\"id\":\"a^a8df6de7-dee6-43d3-81ec-1959cac89c53\",\"title\":\"To move from place to place\"},{\"id\":\"a^e2edff77-9831-482d-9ada-85fb12a25128\",\"title\":\"To move and never return\"},{\"id\":\"a^d246d91b-84e7-4253-813b-0ae26ca88cf2\",\"title\":\"To move communities\"}]}",
			"size": 1000,
			"type": "list_picker/button",
			"sort": 1
		}, {
			"id": "3",
			"contentType": "text/plain",
			"data": "[{\"type\":\"text\",\"text\":\"Question\"}]",
			"size": 1000,
			"type": "header",
			"sort": 2
		}]
	}
}

works.json

{
	"message": {
		"receivers": [{
			"name": "name",
			"address": "917358445777",
			"Connector": "917358445777",
			"type": "individual"
		}],
		"parts": [{
			"id": "1",
			"contentType": "text/plain",
			"data": "[{\"type\":\"text\",\"text\":\"When you want to get the goods which have just arrived you go to ...\"}]",
			"size": 1000,
			"type": "body",
			"sort": 0
		}, {
			"id": "2",
			"contentType": "text/plain",
			"data": "{\"buttons\":[{\"id\":\"a^441ce058-b497-4bf5-b91c-38a6384214d3\",\"title\":\"The shipping area\"},{\"id\":\"a^a8f5af15-70a5-4c93-b765-eaf43b446c59\",\"title\":\"The storage area\"},{\"id\":\"a^c173b0b2-7f7b-4ee8-aab8-7d44a01fdd7c\",\"title\":\"The loading area\"},{\"id\":\"a^2c2d68f4-fb58-4044-aa0c-c5dca009eb30\",\"title\":\"The reception\"}]}",
			"size": 1000,
			"type": "list_picker/button",
			"sort": 1
		}, {
			"id": "3",
			"contentType": "text/plain",
			"data": "[{\"type\":\"text\",\"text\":\"Question\"}]",
			"size": 1000,
			"type": "header",
			"sort": 2
		}]
	}
}