Problem with railways

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Running Exp9.2 and latest version of Pak128.Britain-Ex (version not shown anywhere)
Year 1814 and I do not like the properties of the available rail. I introduce a new type of plated rail, wich is a problem and is not be visible.
So I have to use the one shown, and I layed a short track.
Next idea was to alter the existing pak-file.
To sort out the right one I extracted Britrail-Ex and removed the Pak-file with the corresponding name.
Normally you cannot, after doing this, save and reload.
It is however possible. The railroad is still existing. The name of the track is different, but the properties are still the same.
This procedure of removing and checking can be repeted until there is only one, the tgv.Pak, left. After removing also that one, loading is not possible any more.
Can anybody explain this?
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