Hey
@Gomaruana , the capacitor(s) could degrade over time. The standard ZVS circuit layout is extremely robust. It takes a lot to kill it.
The only smoke I've ever seen come from the components is from particles of flower or condensed oils around the coil.
There are two types of degradation, however; 1) Over-use of a specific components and 2) Different vapcaps. Some vapcaps you simply cannot push a lot of power into where other caps will rail the supply current. Measure the voltage at the ZVS board and monitor this for changes.
If you are running batteries, check that cells aren't changing their internal resistance. I have some end-of-life cells that have a huge voltage drop when firing.