Q.Butterfly bush
A large stem of my butterfly bush “rotted”. It feel off in my hands. Inside seemed to have a couple of beetle like bugs. The rest of the plant seems strong. Any suggestions? Do I hav e a problem?

The soil may be overly wet if you had issues with rotting stems. Make sure the soil is well draining.
Though Butterfly Bush is quite pest resistant, it can be infected by pests such as Japanese Beetle, Spider Mites, and Aphids.
Treat the plant with Neem Oil. Neem Oil is organic and safe for people and Bees.
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm