Hi all. I've had a similar experience with my Gates-based Cube Hyde.
- There is a chance the belt's teeth are contaminated - try brushing the belt using e.g. an old toothbrush to make sure exclude all dirt and sand as culprits. You use water + soap to do it.
- A temporary fix for squeaky belt is rubbing soap or candle (i.e. wax) into it. Do NOT use any lubricants like grases or WD-40s as it could damage the belt.
- I also noticed that the belt stopped squeaking in rain.
No matter the method, the squeaking always returned after a week or so.
Because I tried to rule out everything, I ended up replacing my old squeaky
pedals (bought some Shimano Saints) and then replaced my
Bottom Bracket, which cost me a lot of money and time (the old one was hard to remove).
Ultimately, it turned out the front Carbon Drive sprocket was pretty worn, and some teeth were wafer-thin. This was the source of squeaking. The moment I replaced the sprocket all the squeaking went away.
For CenterTrack there are two options:
CDX and
CDX:EXP - the latter sprocket is more expensive and made of more durable aluminium alloy.