Truck freight is the most abusive way to ship in my opinion, if the shipment ever crosses thru a freight terminal. I've been to a few in my life, mostly feared for my life with the forklifts running basically wide open throttle forward and reverse, seen some seriously damaged stuff and gotten some damaged stuff from them stacking things on top of other things.
That said your best insurance for any shipping method is a full 3/4" plywood crate.
That said, I would find a big cardboard box which fits the machine, build the custom crate out of 3/8" ply or osb and 2x2s, and then slide it into the cardboard. Mega tape and you are off.
I might have covered this with someone else in another thread, but if it were you, sorry for doubling up - and of course, opinions and experiences vary...not arguing, etc.
In my experience, especially for heavy or bulky stuff, LTL is a way better option than UPS/FedEx package delivery, but you have to crate or pack it securely with what you said above in mind. If they can knock it off the pallet, they will, but IMO you did not do a good enough job crating. But if it stays upright and doesn't break up, it will probably arrive just fine.
A customer bought an engine on eBay shipped direct to us and all the shipper did was set it on a pallet, wedge some 2x4's under the flat parts and throw ONE steel strap over it. It arrived upside down and leaking all over.
Another customer bought a crate engine and it came packaged, well, in a crate. A very well constructed crate. The engine sat in a 2x8 "box that held it by the oil pan railed, then it was bolted via the motor mounts and also strapped down with steet strap in multiple places, all this before a crate being built around it and it clearly marked "no stack".
Its all in the crating/packing.
Final example, possibly more relevant - we use magnetic sheeting of various colors to produce on of our main products. It normally ships UPS/FedEx. A 24"x50' roll weighs 75#. When we get the rolls, the cardboard packaging is smashed with no remaining 90 degree corners left. The manufacturer plans on this and the packaging protects the product, but dies doing it. It is obvious they drop it every time they handle it.
Occasionally, we buy 3-4 rolls at once and they ship LTL. It arrives on a pallet, strapped down with 1-2 plastic straps and the boxes perfect condition.
That kind of illustrates how the respective "systems" handle heavy packages to me.
DaveW