Thats my thought. If you walked out 5 mins in and explained the reason then most staff would refundYeah. It seems like the cinema might be a bit funny if you stayed for the whole thing, since it's basically saying, "This was wrong but I watched it all anyway". You couldn't have known the dub would be fixed in later showings but equally you did watch a whole screening which is what your ticket was for.
If you watched the whole thing then asked for a refund I would think you were taking the mick