Spinning wool which was once common in almost every rural household is becoming popular again as a way to reconnect with the past

Had to look for the missing details to this question and here is my answer.

Based on the underlined parts of this sentence, the erroneous part I can say here is "Spinning Wool". What makes this erroneous is that it misses the necessary article which is "the". This is very important in the sentence as this emphasizes the subject which is being described in the sentence.