Do you have experience smoking meth? This is pretty normal if you put a lot in the pipe, and then use too much heat, it'll happen a lot if you are sharing and some dickhead is trying to smoke the whole bowl in one hit and keeps the lighter on it. You want to heat it up just to the point of vaporization then keep rolling it back and forth, only re-introducing the flame intermittently to keep the temperature in the sweet spot, if you keep the flame on it after vaporization begins it will turn black, instead of just brown and oily.
Meth is a lot less cut than paranoid speed freaks make it out to be, especially if you are getting it in nice big shards. It might not be walter white pure, but people REALLY overestimate how much meth is getting cut because you can't just re-rock it like heroin or coke, and it's already dirt cheap, you'd need something that looks like shards in the first place, now if you are getting a bag with a bunch of powder in it or obviously has differently textured substances in it, then don't buy it...but other than people trying to pass off some bunk, like MSM or rock salt, in my experience meth is usually meth although you would never believe that if listened to spun out dopeheads. In the rare case that you do run into something stepped on, not just straight bunk, most cuts won't liquify and vape right, they will char instead of melt, and even if they don't char then you won't be blowing thick clouds or the taste will be wrong.
Since you mention cleaning the pipe, trying again, and it looking like caramel, that sounds about right, maybe more amber than caramel and still translucent, the more you overapply the heat the darker it will turn and if you are putting a lot in the pipe and re-heating it over and over its just more chance to overheat it.
Another thing you can do, is right after you load up a bowl before you start to actually inhale it melt it down with light heat and spread it out, this will prime it for smoking as to avoid having a bare spot of glass getting too hot and then your melted meth running into that bare spot and immediately overheating.