Such munitions have a shelf life and most of them were produced, at the latest, in the early 1990s. Most are far, far older.
Typical shelf life for a cluster munition is maybe 20-30 years until it stops being even vaguely reliable.
I leave it to the reader to do the math on the amount of time that has elapsed since 1993 to today.
Those supposedly unreliable old munitions are killing many Russian soldiers. The videos of strikes with the munitions show a situation no infantry troops want to be in.