The convection oven market is still very new and little is known about, which is safe and, which is not as independent review have yet to occur in any volume as the DYI group have not had reason to open one up.
The technology in North American designed, but built is China. Organizations that are interested in protecting their name are likely safe.
Remember that 'ptfe free' means nothing as ptfe 'was' a patented product that 'was' easily walked around by making minor changes to the formula, which allow less than honest companies to legally state they are ptfe free!!
If your product uses a coating on coils, it could be a problem.
It will likely be a few more years before the truth is know for certain.
Sorry for the lack of clarity, but it is what it is at this point.