You have put glue into the threads, that is the problem.
What you did wrong was to spread the glue inside the shaft and then push in the insert.
basically you used the insert to push the excess glue before it, up the shaft into a big glob onto the back of the insert and so enter the insert threads through the hole in the back of the insert.
Next time, screw a field point onto the insert, and then spread your epoxy mix sparingly around the body of the insert.
As you push in the insert this time, the excess glue is now pushed out of the shaft, where it can be wiped off with some paper towell.
What you need to fix your current problem, is an eight guage, 32 threads per inch, bottom, tapping tool to clean the glue out of your insert threads.