Withholding bowel movement

[Helen71price]

My granddaughter is 4 years old and since potty training we were having trouble with her withholding stools then she got a lot better and she was regular with no problems at all, she eats a very healthy diet and is not constipated but she does produce large stools which is why I think she tends to withold, we do give movacol to keep her regular and soft but sometimes goes too loose, any help or advice would be much appreciated, like I said earlier she goes really well but if for any reason she produces a large stool it sets her back 😪😪😪