@Tommy Tam Internal size limit for the XML transform action is 100MB. The XML from the trigger is base64 encoded and some content gets added for transform, so the final size gets increased.
Note: If your file is smaller ~70MB then also you might observe the same issue as mentioned above as it is base64 encoded and some content gets added for transform.
There is no option to increase the size limit of the connector, to workaround try splitting the XML into multiple files of smaller size (< ~60MB) and process.