Can you tell me if mixing suboxin with methadone have any bad consequences?

YES: Suboxone contains Buprenorphine and naltrexone. The first is similar to methadone, but the second, will block the effects of methadone. So, taking them together can lead to or cause a partial withdrawal from the opiates. Normally, it is best to separate the use of these two drugs by 1 to 3 days. Otherwise, instead of a relief from pain or withdrawal, it can cause it!