Thanks Ill try thatI have the same airbrush and have had exactly the same problem time and again.
Recently the brush started performing better after I bought an ultrasonic cleaner.
You can get them for about $30.00 on Amazon.
Disassemble the brush completely and put all the parts in the cleaner. Let the cleaner run for a full cycle or two to give the brush a thorough cleaning.
And each time you use the brush run AB cleaner through it immediatley after use.
And as others have said, make sure the needle tip and other parts of the assembly are screwed in properly.
Each time I take the brush out now I test it before adding paint. I still have to put it in the ultrasonic cleaner now and again to make sure it stays as clean as possible but most of my problems have now been fixed.