It is possible it was an old batch of pills or maybe they had been exposed to extreme heat or cold for whatever reason and this can change the chemical comp of the med.
It is hard to say but you may try going to methadone anonymous site and they may know more and they also will be able to assist you with going onto the sub-x as they have lots of folks on that as well.
2 knee replacements & a hip.
spondylosis at L-4,5 & S1
arthritis,sciatica all that being a CPer entails!
If you stumble make it part of the dance!
Formerly Ruth Thomas