One of Fortnite’s biggest draws is that it’s constantly updated with new things, like limited-time events or fancy weapons. While the steady drip of tweaks and additions help keep Fortnite fresh, it’s hard to predict how all these different elements will interact with one another. Lately, players have been exploiting a Fortnite vehicle in a way that keeps forcing Epic Games to take it out.

Shopping carts were introduced into Fortnite on May 30th, and they were an immediate hit. Players could drive carts, or could push them around while other people enjoyed the ride. Better yet, fans could build elaborate ramps and traps that turned matches into amusement park rides. It was messy and ridiculous, yet very Fortnite.

But two weeks later, on June 11th, shopping carts had to be disabled. Then they came back on June 14th. Two days later, shopping carts had to be taken out of the game once more. Then, on June 20th, shopping carts came back. Two hours later? They were gone again. For players who enjoy riding around on shopping carts, the whole thing has been like a seesaw: you never know if they’ll be useable or not.

Due to ongoing issues, we'll be disabling Shopping Carts again. We'll update you when this issue is resolved. — Fortnite (@FortniteGame) June 20, 2018

So, what’s going on? While Epic Games has repeatedly tweeted that shopping carts are causing “issues,” a representative clarified to The Verge that the problem is that players keep using them to go underground, beneath the maps. There are YouTube tutorials out there with hundreds of thousands of views showing this glitch in action. Previous methods include building a structure and repeatedly grabbing a shopping cart while standing inside the structure, and grabbing a shopping cart while sliding down a mountain. While under the map, you can die by the storm — but you are also impervious to damage. You do, however, have to take care not to fall to your death by continually building platforms under you.

Most recently, the method that seemingly got shopping carts disabled is that players could get under the map by building a pyramid over the vehicle. Other videos showcase different methods to do the same thing, though often getting under the map leads to death. Now, getting under the map in itself isn’t the issue. The problem is that anyone using the exploit can still clearly see and harm other players above them. So you could be in a match where an invisible, unreachable force suddenly kills you out of nowhere:

Players have reported that killing people while under the map has led to bans, and of course Epic has continued to patch out methods as they come up. But players keep finding new ways to abuse the shopping cart, so it’s become a game of cat and mouse.

Normally, when new additions aren’t working out the way Epic intended, the developer usually “vaults” items — that is, takes them out of commission for the foreseeable future. While we don’t know if this is the future of shopping carts necessarily, it seems unlikely that Epic wants to get rid of them.

Since they’ve been released, shopping carts have quickly become a fan favorite that showcase everything that makes Fortnite so joyful. Epic can’t just get rid of them without disappointing fans, which might explain why the feature keeps leaving and coming back. Instead of decommissioning them, Epic wants to find a solution. Now if only players could stop finding new ways to get under the map.