@hrb264
I've managed to find and fix the issue. The error is complaining about there being an extra character after the final "e" in the Lemmings Stampede pack name in the levelpack.ini file. At the top where it says name =, there's a space after the final "e," which throws the error in the image you posted. I've removed that space and resaved the levelpack.ini and now everything is fine again. There's also a space after the final "e" in the # line at the top, but I'm sure that doesn't matter, as any line indicated by the # symbol is a comment, similar to how computer programming languages work. In any case, I went ahead and removed that space in the # line as well. Just goes to show you how very picky RetroLemmini is, where even a single mistyped letter and/or a single extra character is enough for it throw a fit and complain!
I've reattached the fixed levelpack in the OP. Alternatively, you can just download the levelpack.ini file I've attached here and simply put it in the resources/levels/Lemmings Stampede folder and overwrite it when prompted.
I've managed to find and fix the issue. The error is complaining about there being an extra character after the final "e" in the Lemmings Stampede pack name in the levelpack.ini file. At the top where it says name =, there's a space after the final "e," which throws the error in the image you posted. I've removed that space and resaved the levelpack.ini and now everything is fine again. There's also a space after the final "e" in the # line at the top, but I'm sure that doesn't matter, as any line indicated by the # symbol is a comment, similar to how computer programming languages work. In any case, I went ahead and removed that space in the # line as well. Just goes to show you how very picky RetroLemmini is, where even a single mistyped letter and/or a single extra character is enough for it throw a fit and complain!
I've reattached the fixed levelpack in the OP. Alternatively, you can just download the levelpack.ini file I've attached here and simply put it in the resources/levels/Lemmings Stampede folder and overwrite it when prompted.

It looks like I've unlocked a new life quest too soon. 

In any case, same situation as you, that it isn't cancelled in any way and that I'll keep working on it for as long as I can until it's finally done and released whenever it's ready