Netty when configured with reuseChannel=true invokes wrong AsyncCallback. It invokes callback registered by first netty invocation in given route multiple times. This can be observed by debugging NettyReuseChannelTest. This seems not to cause serious problems at least in simple cases, because both callbacks (from SendProcessor) do not do much and simply continue routing. I am not sure if in more complex cases this could cause more problems.
However there is one observable issue caused by this behavior: event notifications contain wrong endpoint and wrong time taken. I attached a test for it.
Another problem is that this behavior makes it harder (if possible at all) to fix
CAMEL-16178 for case with reuseChannel=true.