Implementing an interface like that isn't trivial. The signatures of those methods also vary depending on the aspect instantiation model you have chosen (default singleton, but it could be pertype, perthis, etc). And it is a shame for you to have to do that when the generated implementations are just fine. Other instantiation models also introduce further methods beyond those two.
The intention is that the only time your @Aspect is going to be used is when weaving so it is isn't unreasonable for AspectJ to add those methods. In old AspectJ versions we just to hunt for these things and finish them off but finding them proved very costly. In more recent AspectJs you need to tell us about them up front and make sure none of the exclusion filters would cause them to be ignored. Something about your setup is causing them not to be finished off - possibly a bug but it can be configuration (accidentally causing them not to be included for weaving). As you saw, it worked ok for my simple scenario with the LTW agent, so we need to understand how your setup differs from that. If you can create a minimal scenario that doesn't work, like mine, then I can debug it.
cheers
Andy