More technical details about the Mastertronic release
The disk seems to be mastered and duplicated in two different devices. The regular tracks (0-78) on one hand seem professionally duplicated. While the copy protected track, track 79, seems to be done separately. This track is not a faithful reproduction of the original copy protected in the Epyx release, but a manually crafted track that emulates the protection yielding almost the same result.
I'm not sure why it was done like this. May be they used cheap duplicators that couldn't handle the protection. May be they didn't have the original master to make the protection. Btw, this was quite common in the later generation of budget releases. We know they even sometimes used cracked versions. But it unusual, to say the least, on a Mastertronic release that shouldn't be that late.
The original protection is based on a couple of overlapped sectors (one sector embedded in the other) in such a way, because of their content, that it can't reproduced exactly with the standard FDC on the ST. In this case, in this budget release, this was replaced with two separate, non overlapped, sectors. And then this can be written and created with a plain ST. In addition, and because this take more space, they shortened the two first sectors. As you can see, a manually crafted track that when is read by the game it reads almost the same as the original. But they made a small mistake when crafting the track and the data is actually not identical as the original, so the protection test fails.
It is possible that this protection adaptation was made by Mastertronic, or somebody they hired. It is also possible they simply used a non original copy, a pirated copy that copied the original release with a software copier like Procopy. The latter might make more sense when you consider that the disk has a deleted saved game. But even then, it still seems that duplication of this track was performed separately.
In addition to this, when the game checks if the protection test failed, it crashes. That's at the point where on the original release it just makes more difficult to beat the enemies. I don't know exactly why it crashes and as I said, I'm not very motivated to investigate it. It doesn't seem to be related to the protection test fail. The point is that the protection test fails, even with TOS 1.0. And, in addition it crashes. The actual program was altered, so may be there was an attempt to crack it or at least modify it.