Affected users see the following message: "A new iOS update is now available. Please update from iOS 12 beta." The problem is that users who receive this message are are running the latest version of iOS, and there is no additional software to update to.
Beta tests have seen this popup since the last beta was released August 27th, but during the last day the popups have become much more frequent.
Many users now see the popup every time an iPhone or iPad running beta is unlocked, and it's a popup that must be rejected manually every time an iOS device can be reached.
Developer Guilherme Rambo has suggested that an error in the latest update gets iOS beta to believe the expiration date is whatsoever, which leads to the popup issue.
It appears that this method in the Springboard makes some date / time calculations to determine if the current building is about to expire whenever the cover is rejected. For some reason, the latest buildings in IOS 12 believe they are about to expire. @ davedelong : P) pic.twitter.com/HWe7C0NnIT
– Guilherme Rambo (@_inside) August 31, 2018
Complaints on Twitter and MacRumors forums are retrieved from users who are frustrated by losing their popup and it is not clear when a solution will be available.