It is really hard for us to analyze and critique your method remotely. We would like to, but we dont want to spin you around with a bunch of wild guesses that might leave you more confused than when you started.
There could be some component of these pills that does not lend them to effective vaporization. Again, I'm really not sure and it will be ver difficult for us to figure it out from our phones.
I know it isn't the advice you want, but I think you would be best off and most satisfied by using an alternate route of administration. You're lucky actually, as Oxycodone had one of the most favorable ROA ratios of any of the commonly prescribed Opioids. For instance:
Morphine is about 1/3 the potency orally as it is by injection, as us Diacetylmorphine (Heroin). One of the primary reinforcing characteristics that draw Heroin users to injection over say, insufflation is the financial benefit. When you tell someone they can reduce the cost of their drugs by 1/3 instantly, it can be hard to convince them to keep insufflating.
Oxycodone is generally quoted as being ~80%-90% or so by the oral route. So, people who inject or vaporize Oxycodone are doing so more for the "rush" than for the economic benefit. I
Injection and insufflation as ROA's lead to more complications than simply taking the drug orally. From a Harm Reduction perspective, we have to advise alternate, less dangerous ROA's.
I would consider rectal administration. It is a means by which you can experience a faster onset, more of a "rush" etc. without sacrificing bioavailability and without all of the potential complications associated with both injection and vaporization.
So, case in point, we won't be able to accurately tell you why your vaporization efforts are not working, but we can advise you on easier to execute and more effective and safe ROA's such as rectal administration.
Any questions you may have, we will try to answer.