If that's not an option, consider there are three main possible causes for your problem:
very bad solder joint from the cord to the driver
some sort of obstruction between the driver's acoustic output
a defective driver
In the latter case you have to find the replacement driver; in all three you have to break open the casing. It seems to be made of two machined aluminium halves joined by pressure or maybe a thread. In either case taking them apart doesn't look easy - I tried to twist mine with a pair of pliers but didn't put too much torque lest I break or crush the stem.
Bought them new and they came in already opened box and used, so I got refunded and kept them.
Curiously my Pro 900 also have this problem sometimes.
It will probably be almost impossible to open the case without breaking something inside and then putting it together again. And i doubt Astrotec themselves would repair it, and even less that it would be worth it.