Hi Robert,
Fortunately, I haven't come across this problem yet when cleaning.
As Doug suggests, this is fundamentally a problem that occurs with cheap, imported product.
Years ago, the cheap foam that was applied as a secondary backing used to send some dogs into a chewing frenzy, due to the smell it emitted.
Due to the types of properties I clean, I don't expect to come across this anytime soon, but it's worth looking out for, as for solving the problem, if John Kelly hasn't found a solution yet then I doubt if one exists.
One of the reasons I choose to stick with established British manufacturers when I supply carpets, is the knowledge that the products they use in the manufacturing process will be consistent, they won't try and save a buck by using sub-standard materials.