I have a similar problem with the Hotwax. The Crayon overdrive drops its volume after a while and the overdrive sounds really shitty. ‘Have you tried turning it of and on again?’ – Yes I did, and it sounds great again. But after a while the same thing happens.
I returned it to my dealer and they say it has been replaced by EHX. But the replacement has the same problem. I doubt it if it has been send to EHX. Could you check if it has been send and replaced by you?