Replace the bit, tighten up the collet nut and throw the lock back forward. The lock has to be down in order for the RTX to start. Performance wise the RTX is right on par with other rotary tools. With the exception that it has a higher minimum speed. This may cause a problem when cutting softer materials such as plastic.
Speed generates friction which generates heat which causes melting.
This may or may not be a problem depending on the material you use. Personally I have not encountered this problem. The RTX has twice the amount of power and torque as other rotary tools, this means that there is no bogging down and the job can get done faster. While visually identical to the Dremel's it is much weaker. I was changing a cut-off wheel and broke the mandrel by tightening it too much.