Just to share with you guys my experience.

I had problems with my bps. It was unstable and bba started to appear. I figured that my needle valve was faulty as I couldn't fine tune it to my preferred bps. Brought my solenoid regulator to NA and got my needle valve replaced. The problem still persisted. Took apart the regulator to see if there was any blockages or whatsoever and still no answer. Then I took the regulator and CO2 tank to my other planted tank. Plugged the other CO2 set up (CO2 tubing,check valve, diffuser) into my "problem" solenoid regulator and guess what? My "problem" solenoid regulator was working perfectly. The bps could be fined tuned with ease. So my point here is, if there are any of you guys who may come across this problem in future, sometimes, its not the needle valve which is causing the problem. It may come down to the CO2 tubing which may have been used for a very long time and is in need of a change. I suspect that there may have been a leak somewhere in the tube.