Hi Brad,
You can certainly obtain earlier versions of our premium plugins here (and earlier versions of The Events Calendar itself here).
I don’t recommend downgrading – and, since you will be reintroducing bugs that have since been fixed, the amount of support we can offer if you choose to follow that path will naturally be more limited for as long as you stay with an older version – but the choice is ultimately yours 🙂
Remember that there will still be potential for other issues to surface from the same problem (which is that your theme calls an undefined function within the footer, stopping further code from running). It might be in a lot of cases you can “get away with it”, but it’s definitely something to be mindful of.