77 impressions and 1 sale is 1.3% conversion, which is below typical but not impossible depending on traffic temperature. A few things worth checking before assuming shaving.
First, is this the same traffic source as your previous 4 years? Order form conversion is extremely sensitive to traffic quality. Cold SEO traffic will convert far lower than warm email or retargeted visitors.
Second, check the gravity score on the offer. If gravity dropped significantly it means other affiliates are also seeing fewer sales, which usually points to the offer degrading rather than shaving.
That said, ClickBank shaving is a documented issue going back years. The cleanest way to verify it: run a small paid traffic test and track server-side with your own pixel alongside ClickBank's. If your tracking consistently shows 20-30% more conversions than ClickBank reports, that is shaving. If the numbers roughly match, the issue is traffic quality.
If you confirm shaving, the fix is moving to direct vendor partnerships with their own affiliate tracking through Thrivecart or PayKickstart. Cuts ClickBank out entirely.