import re
regex = r"^\d+\s*Order\b.*(?:\n(?!\d+\s* Order\b|.* Truck$).*)*\n.* Truck$"
s = ("\n\n"
"1 Order \n"
"order1 stuff\n"
"order1 stuff\n"
"etc\n"
"ShippingMethod: Truck\n\n\n"
"2 Order\n"
"order2 stuff\n"
"order2 stuff\n"
"etc\n"
"ShippingMethod: Truck\n\n\n"
"Order Summary\n\n")
print(re.findall(regex, s, re.MULTILINE))
aW1wb3J0IHJlCgpyZWdleCA9IHIiXlxkK1xzKk9yZGVyXGIuKig/OlxuKD8hXGQrXHMqIE9yZGVyXGJ8LiogVHJ1Y2skKS4qKSpcbi4qIFRydWNrJCIKCnMgPSAoIlxuXG4iCgkiMSBPcmRlciBcbiIKCSJvcmRlcjEgc3R1ZmZcbiIKCSJvcmRlcjEgc3R1ZmZcbiIKCSJldGNcbiIKCSJTaGlwcGluZ01ldGhvZDogVHJ1Y2tcblxuXG4iCgkiMiBPcmRlclxuIgoJIm9yZGVyMiBzdHVmZlxuIgoJIm9yZGVyMiBzdHVmZlxuIgoJImV0Y1xuIgoJIlNoaXBwaW5nTWV0aG9kOiBUcnVja1xuXG5cbiIKCSJPcmRlciBTdW1tYXJ5XG5cbiIpCgkKcHJpbnQocmUuZmluZGFsbChyZWdleCwgcywgcmUuTVVMVElMSU5FKSk=