I just sent this email to @mattellis70, but it's useful info so I'll post it here too. When the unit is cooling slowly, a few things could have gone awry: the jacket, the chip, or the rod:
Jacket: Usually what will happen if there is a problem with the jacket is the unit will cool on spec until it essentially hits a wall, as it appears to be the case with Matt's. There usually isn't a gradual slowdown, it just stops cooling at a certain temperature. This is more common in conicals if the brewer didn't get the velcro all the way fastened leaving a gap exposed. If you have this, try feeling around your insulation and see if you can find any gaps. Check around the base as it's comprised of a 15" circle cut out of insulation that your fermenter sits on and large walls that wrap around it.
Cooling chip: these are usually an all or nothing failure. If the fan turns and your rod isn't cooling at all, then the chip is most likely dead. These can sometime have partial failures where some of the semiconductors go out and the cooling rate can slow, but this is much less likely. If you have a kil-a-watt or similar power meter, plug your unit in and see how many watts it draws while cooling. It should be between 90w and 110w, then slowly decrease as the unit reaches a steady state, approx 80w to 95w. If you are heating, it should be between 25w and 35w.
Rod contact: if the rod isn't fully screwed in or if there is matter between the rod's contact and the cold plate, the rate of cooling can be degraded. Try cleaning out the contact point and screwing it back on.