Does it make a difference what speed you are using??
I believe the electronic speed control module on your router has died. My research shows that this is a common issue with the 7518. My 7518 works fine on the highest speed, but bogs down on low speed. The speed control module is available online at ereplacementparts.com, but it costs $125. Instead of repairing mine, I invested in a Triton router. Now I use the PC 7518 for bits that can spin at top speed, and the big Triton for Panel-Raising bits. You can never have too many routers.
The speed control module on the 7518 was first-generation technology and was never as good at speed control as the newer models such as the Triton.
“We should be careful to get out of an experience only the wisdom that is in it and stop there lest we be like the cat that sits down on a hot stove lid. She will never sit down on a hot stove lid again and that is well but also she will never sit down on a cold one anymore.” - Mark Twain