Is this sentence grammatically correct? Please share your insights [closed]
"Which" in a non-restrictive relative clause can take a sentence as antecedent. In your example, taking the antecedent of "which" to be the sentence "the number of potato products peaked in 2019" makes the example grammatical. The problem is that it is not the peaking of the number that is an increase, but rather that peak number in 2019 itself which is an increase.
So in the sense which makes it grammatical, the example sentence is slightly incoherent.