I had a similar problem with mine. Fine at first, then crackly.
I spoke to DV247 (who I got mine from) who said it could be a dirty pot. I told them I was happy to give them a squirt with some contact cleaner, but would this void the waranty? They were happy for me to try this, so I did. It helped a lot, but still not perfect. It cleared the crackles but the amp was not very loud until about 1-2 O'clock on the vol pot, then at after about 3 O'clock a bit of background white noise. Sent it back to DV247, who sent it on for repair. Got it back 8 days later as good as new. It's still got background noise after about 3 O'clock, but I've since been told the all do this and upgrading the valve sorts this.
As mine is only a couple of weeks older than yours, could be a batch of faulty pots?