Mystical Dispute appears to cost one mana in your hand, but more importantly gives you priority even when your opponent casts a non-blue spell (even when you only have 1 blue mana open). That is basically you telling your opponent you have it...
Hello! I just confirmed this bug will be fixed in the next release. So, hang tight, the fix is on the way.
In general, because of all the work required in releasing an update - testing, staging, deploying, etc. - we usually only do one big release per month. That testing phase can actually take weeks after "stabilization" i.e. no more bug fixes, so sometimes things stay unaddressed for longer than we would like. It's definitely frustrating for us devs as well to have completed the work that's not live yet, but without proper testing, there would be many more problems.
Thanks for the feedback and keep on bringing things to our attention. I try to read through the posts here most days and make sure nothing has slipped through the cracks.