There are a number of items of concern I have been finding while performing maintenance, modification or troubleshooting calls lately. One is loose insulated caps or as some may know then as Marrette connectors. They can make for some very serious problems the least of which might be a circuit failure to the worst being a melt down and/or a fire. If they are not applied properly and tightened properly then they will fail. Usually I find these problems on DIY work. How can I tell? Well usually the tip off is that they are using a mix of different types of connectors or they are placing too many wires under the connector. Like anything else you have to read the manufacture’s application guidelines. when using these innocuous little devices.
The second issue I have been finding a lot of is failed wire connections in backwired receptacles and switches. What I see is where the wire fails at the surface of the device where the wire enters the connection hole. These can lead to intermittent operation or circuit failure to again if arcing occurs. They can be difficult to find especially if they are intermittent. I find I have seen enough of these failures that now use the side terminals at all times. Besides, have you ever tried to release a backwired conductor from one of these devices?? A real pain.