Well, I think the response with helpful suggestions has been great. I think, after all the time I have spent on this issue, that John Ford is probably on the right track. I will certainly look at all the suggestions that have been made. I have attached a zipped file containing some songs that work as I had expected and some that don’t. Those that do work are prepended with ‘!y’ and those that don’t are prepended with ‘!x’.
I have done nothing more than Open Special > Open Midi File.
There does not appear to be any settings that can alter the alignment. I would be really interested if anybody could have a look at the files and let me know their opinion. If this is a copyright issue then I apologise to the holder; I have no intention of using these files, I’ve had them for years and just searched through for examples of what I meant.

https://drive.google.com/drive/folders/1U7-l7o7O5z_D3GsDVcydRalzM2QeQlY8?usp=drive_link