Hi pnw-smoker;
Welcome to the forum.
This is does not appear to be normal functioning of the smoker. Is the circuit that the smoker is plug into being shared by other appliances, such as a refrigerator, air conditioner, fans etc. If too many appliances are drawing power from the same circuit you could experiencing voltage drop, and not enough current is getting to your smoker. If this is the case try unplugging some of the appliances while you are smoking; if that is possible. If you are using an extension cord use the shortage cord possible, and make sure it is at least 16 gauge.
Or you can transfer the food to you kitchen oven. I know it hard to have the oven running on a hot summer day, but you will get better result then leaving the ribs in the smoker at such a low temperature.
The answers to FLB's questions would be helpful:
Assuming the second case, is the heating element glowing red ? Make sure the tower plug is in there good and tight.
And if it is glowing it should be bright read except for about an inch or so from each end.