Reminder: a solar charge controller makes power
In most cases the system is working as designed but the owner doesn't know it.
If no power is demanded then no power is produced. This can happen when
Charge-and-stop usually charges to 14.2v or 14.4v then stops until nank voltage drops to 13.2v before restarting Bulk charging. This occurs because charge-and-stop does not use a Float setpoint.1)
Under very light loads this would result in cycling between 90% and 100% state of charge. Because of voltage sag heavy loads might result in cycling between 95% - 100%.
If this is undesirable behavior you can set up a USER profile with whatever setpoints you wish (suggested settings).
…because of temperature extremes of excessive charging voltage. (lithium only)
It's rare, but sometimes things happen. Fuses pop. Branches reach under and disconnect solar cables Parts fail.