sorry to hear about your experiences. I have 4 Jebao products, it's kind of hit or miss but there is definitely no customer service and the specs on the products aren't always correct.
DCT3000 Pump - Stated that it went down to 700 lph however a simple test showed that it only went down to 2000 lph. No response from Jebao on question about this or my other question about using a less powerful wall wart. Used in larger tank and pump working fine for 1 month now
DC1200 Pump - had a vibration, no response to question about what to do. Eventually went away and pump working for 2 months now.
Jebao Doser. First unit had dead pump, next unit works fine.
Jebao wavemaker - over 1 year, no issues. BTW, if yours it too powerful, you can use a smaller power adapter. This doesn't seem to work with the DCT pumps though.