Hi
I was not successful to replicate this issue and even I could not find anything about it. So sorry that I cannot help. Can you open ticket with Microsoft on this? Seems like your statement is true but I do not know how to solve it.
These are some random questions mainly to see if it can help you.
Do you have any specific customization for TO?
Does user has a permission to ship transfer order?
is this a new error after upgrade or installing any new app?
Do you have all the following setup in Inventory Setup page?
Have you setup those parts in both locations?
Do you have bin setup in Transfer From location?
Do you have bin setup in Transfer To location?
Thanks

Thanks