Thiel Tweeter issue

Is/are the tweeter(s) damaged, or are you just trying to change the sound? What amplification are you using? How large is your listening room?

O.K., The CS 1.2's even with their 4 Ohm nominal rating are not that challenging a load for a Thiel. Still, that can be a struggle for many if not most receivers. Do check to see if your receiver is up to the task. Better amplification might be in order.
Keep in mind that though the CS 2's are floor standers, they're still only 2 ways. Driving them too hard for increased volume levels with am amp not up to the task will cause the amp to clip, which can cause just the kind of damage you've described. It would be a shame to have the tweeters repaired, only to have the same problem arise again. Appropriate amplification is of paramount importance with Thiels.
Much of Jim Thiel's design efforts were building cross-overs to work with and compensate around the specific drivers that he had custom made for his speakers used in specific models. As such I don't recommend just swapping out the tweeters with another brand that fits, or for that matter even off the shelf drivers from the original manufacturers used at that time that might appear to be the same, but were in fact not specific to Thiels order.