Although Windows 10 has gotten off to a great start by pretty much any metric, Microsoft’s mobile version of Windows 10 has had a pretty bumpy road. Originally thought to be an update for current phones sometime late last year, Windows 10 Mobile is still not available unless you purchase a new Lumia 950, 950 XL, or the budget Lumia 550, all of which were announced in October in New York City along with the Surface Pro 4 and Surface Book.

That does not preclude people from using the new mobile operating system on their existing handsets, because Microsoft offers people in the Windows Insider program access to the pre-release software. Windows 10 Mobile is available for quite a few Lumia handsets, as well as a couple of others like the HTC One M8 for Windows.

For those either with one of the newer Lumia phones, or if you are running on the pre-release version of Windows 10 Mobile on an existing handset, one nasty bug caught me out this month. Windows 10 Mobile includes Data Sense, which originally came back with Windows Phone 8.1, and this system tool monitors all network traffic and reports back usage over WiFi and Cellular. On my own Lumia 950 XL, I noticed I had used more cellular data in January than I had ever used in a single month before. Data Sense let me know that a process called “System” had used over 900 MB of cellular data in just 17 days. Beautifully vague as all bugs are.

Speaking with some other people that use Windows 10 Mobile, I found that it was not an isolated incident. Other users had been reporting the same issue, and in some cases they had used quite a bit more data than this. The culprit, it seems, is a setting which is on by default that backs up text messages to OneDrive, so that you can get them back if you get a new phone or wipe your current phone. It’s a feature that has been part of Windows Phone for some time, and I’ve always left it enabled. Disabling this setting reduces the cellular data usage back to normal. In the messaging app main window, hit the … in the bottom right corner, choose Settings, and turn off Message Sync. To be clear, backing up the text messages should only use a small amount of data, and really it should do it over WiFi only. This is a feature I will re-enable when the bug is resolved.

 

System used 909 MB on Cellular and 2.79 GB on WiFI in 17 days

In addition, Windows 10 Mobile offers a new feature which will back up install apps to OneDrive as well, and that can be disabled too since it may also contribute to cellular data usage, even if things like the Store are set to download updates only over WiFi. This setting is found under Backup settings.

I reached out to Microsoft to see if they were aware of this issue. In the current age of mobile data caps, this can and has caught people out, causing them to have to pay overage charges with their cellular providers. A Microsoft spokesperson said:

“We have received some customer feedback regarding unexpected mobile data usage and are looking into this.”

The fix provided here is unofficial, in that it hasn’t come directly from Microsoft PR but rather through a Microsoft employee on Reddit thread found by Paul Thurrott of Thurrott.com, but it has appeared to fix the issue I was having. In the last 24 hours, my System process has only used 0.5 MB of data. If you are running Windows 10 Mobile, I would suggest you check into this to avoid racking up any charges on your bill.

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  • jiffylube1024 - Wednesday, January 27, 2016 - link

    Funny that this potentially devastating bug isn't really any issue because nobody uses Windows 10 Mobile... Reply
  • MonkeyPaw - Wednesday, January 27, 2016 - link

    MS keeps driving that number of users down, too. I was a die hard WP fan at one point, but you got to know when to fold 'em. MS shot itself in the foot too many times by resetting their app API. They've built no confidence for even the few existing developers. I figure MS will just make their own Android phones soon enough, with heavy integration of their own services. I think it would be more popular than WP ever was. Reply
  • Mushkins - Wednesday, January 27, 2016 - link

    It's not even that. I'm not a big "apps" guy, and I'd *love* one of the new Lumia 950s. They're beautiful phones.

    But they're completely unavailable for Verizon customers. The phones *do not function* on the Verizon network. That's a pretty big chunk of potential customers to abandon. Its 2016, the idea of any smartphone being network locked in a first world country is simply ridiculous.
    Reply
  • Brett Howse - Wednesday, January 27, 2016 - link

    Just to be clear you can buy it unlocked, but it doesn't support CDMA. Still doesn't help you but it's not the same thing. Reply
  • AMRooke - Wednesday, January 27, 2016 - link

    The phone hardware is CDMA capable, but Verizon won't license the 950s on their network, so MS disabled the drivers. Should Verizon ever choose to play nice, MS needs only to push out an OS patch to "wake" the CDMA radios. Reply
  • Brett Howse - Wednesday, January 27, 2016 - link

    Yes the hardware is capable but the phone was never approved for CDMA by the FCC and that was Microsoft's decision to not have that done. So they can't just patch it to enable CDMA without getting all of that sorted out first and it doesn't appear that this is on the radar from what I've found. Reply
  • Alexvrb - Wednesday, January 27, 2016 - link

    The reason for this is that there's no getting around Verizon. If they chose to enable CDMA, Verizon would just block them and stall for many months. They've done it before to unlocked devices. Not to mention it would piss Verizon off and damage the prospects of getting something like a Surface phone on their network in a timely fashion. Reply
  • beginner99 - Thursday, January 28, 2016 - link

    The real issue here is Verizon and CDMA. Not MS or Windows Phone. Reply
  • hrrmph - Friday, January 29, 2016 - link

    +1

    MS is doing the right thing here. Verizon isn't.

    The OP doesn't seem to understand that it is Verizon that is acting like an isolated Banana Republic here by using CDMA in the first place.

    The rest-of-the-world has moved on to better things and Microsoft is moving forward with them.

    So the best thing for MS to do here is leave Verizon and its kind behind. Others should too, if there are viable alternatives.
    Reply
  • Duckhead - Friday, January 29, 2016 - link

    I love my Windows Phone and I'm not an app guy, but there are a few missing apps on Windows Phone that are beginning to annoy me. Mint discontinued their app. I'd like see what all the fuss is about with Snapchat, but they don't have a Windows app. I wanted to buy a Pebble watch, but they don't have an app. I wanted to buy a Nest Thermostat, but they don't have an app. Reply

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