There have been reports that Windows Insiders for Windows 10 Mobile are experiencing rogue data usage that is eating up their data plans, even when a Wi-Fi connection is available.
Windows 10 Mobile is a relatively new mobile operating system compared to iOS and Android, and as such bugs are expected to pop up here and there. The reported issue, however, is not just a mere annoyance, but rather a serious problem that could have users seeing dollars upon dollars going the drain.
Several threads have been created on the Windows Phone Reddit regarding the problem, with one such thread started by a user with a Lumia 830 running the Insider Build of Windows 10 Mobile. According to the user, the smartphone is constantly trying to connect to the network. Upon checking the data option in the phone's settings, System is shown to take up most of the device's usage. The user's AT&T plan have already used 4 GB, with System responsible for more than 3 GB of the consumed data.
The user claims that the only way to prevent Windows 10 Mobile from consuming data is to deactivate cellular data.
Other users have reported that System consumes hundreds of MB daily, which will quickly add up as most subscribers are on a data cap for their mobile subscriptions.
The cause of the problem was believed to have been found by another Reddit user, who claimed that it was the message sync feature that was behind the data plan drains. It seems that the feature is eating up massive amounts of data as it restores backups of years of SMS and MMS through the cellular connections of users, even when devices are connected to a Wi-Fi network.
The user mentioned that to fix the problem, users will have to enter the Windows 10 Mobile device's settings and access the Messaging menu under System. There, the option to sync messages between devices should be toggled off. The user said that this solved the issue after about an hour as tasks that have already been started were finished over the time, with no new tasks added as the feature has been turned off.
For what it's worth, Microsoft's data team is looking into the issue, with the problem being tracked through the feedback app.