Another sign of a foundation issue is cracks in the walls and floor of the basement. It can be due to water pressure from the soil beneath and behind the floors and walls. You know very well it is not a sign to ignore.
This one also needs immediate foundation repair. If you feel your foundation is sinking slowly, contact help and save the disaster.
If a huge amount of water is entering your basement, you shouldn't ignore it and pay attention to its repair. Water floods are a clear indication of something fishy.