Mission 752 'freedom'

[davidsrsb]

Isolate the tweeter and connect it to an AA battery, both ways. You should see the entire dome move evenly.
Dried out ferrofluid usually causes the dome to stick somewhere and twist when you try this test.

Output can actually go up dried out, but with lots of distortion, which REW or Holmimpulse will both show.

 

[AmadeusMozart]

If the tweeters can have their domes/voicecoil replaced "in the field" then you should be able to clean out the ferrofluid and either leave them without ferrofluid or put some other in. PartExpress sells small tubes with exactly the right amount in each tube.