I posted this issue on the site as well, basically after fitting an attachment (in my case a saw head) and dropping in a fully powered Kinetic Capsule the Multi-Tool doesn't work, there's no head visible despite it saying it has one attached, it also has power, but nothing happens.

I have no crash report as this bug did not cause one, I am using buildcraft-6.1.5, Eureka-1.7.10-2.0, BuildcraftAdditions-1.7.10-1.7.1-Jenkins-16. Happy to provide any more needed info upon request.

this is not a BC bug but a BCA bug, could you report it there instead next time?
https://github.com/AEnterprise/Buildcraft-Additions/issues