The issue is baseload generation like nuclear: we can’t switch it on and off quickly; we can’t ramp it up or down fast enough to match actual demand. There are times where we have to keep it online during a surplus, when we know that surplus will drop off and leave us with a shortage.
Combine that with variations between forecasted and actual weather conditions affecting solar and wind production, and yes, we will occasionally have surplus power to deal with.
The long-term solution is better demand shaping methods, to make use of any amount of power in excess of normal consumption. But until we have the ability to switch on loads and suck up such excesses, we are going to have this problem from time to time.