I’m currently having similar sporadic (every month or so) problems (described here: Alexa randomly turns to "device is unresponsive", even though the amazonechocontrol binding is still connected (e.g. Echo_Dot_Speak still works)). The problem can also be solved by restarting openHAB. However, this is not very nice.
Did you figure out the root cause, to avoid having to restart openHAB whenever the problem shows up? How did you identify your problem in detail?