Multiple Draft Invoices getting created

Have a couple of issues:

1) Multiple draft invoices are getting created automatically for a "Full Member" membership. Have over 4000 drafts created automatically. Would like to know what's causing this behaviour.

2) Looking to bulk delete the already created drafts. Seems like via the dashboard, I can only select 20 drafts at a time, which is gonna take a lot of time to delete these 4000+ drafts.

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