Hi hjnicol
That definitely sounds odd. My first guess would be the same as yours - that the portal might be at the end of it's life. Since it's the only one acting up, then I would think something must be off with that particular portal rather than the Gateway itself or the rest of the system. My suggestion would be to check in with technical support so they can take a look at it from our end, and if needed they can book you a service call.