I've only been able to create this bug twice, mainly because I've only done the requirements for this bug twice. Essentially what happens is when you place massive long rows of hoppers, regular hoppers when become PF Hoppers, without you know, and begin acting as a PF Hopper. However, the name when you open these hoppers are still labeled as "Item Hopper". Only when you break it, are you aware that it's now a PF Hopper. It then gives you the message that you removed one, and gives you now a PF Hopper instead of a regular hopper in your inventory. Breaking and replacing these hoppers is NOT a fix. Last night I narrowed down every hopper that was acting as this by deactivating it with redstone, and seeing which ones were collecting crops. I then decided to break and replace all of these bugged hoppers with more regular hoppers and move on. Only about 25% of the replaced hoppers went stayed regular hoppers. The remaining 3/4 of the hoppers kept becoming PF Hoppers, some immediately, some it took a couple minutes to switch over. Screenshots provided below (they're not exactly that helpful so if any staff would like to see for themselves what's happening I have left these hoppers where they are); https://imgur.com/4abePFj https://imgur.com/2YCYGb5
This kinda happened to me as well. I randomly got a pf hopper while harvesting sugarcane and it said I successfully broke a pf hopper, but none of my hoppers or pf hoppers were changed. The extra pf hopper is in my pv currently.
