Random freezes of mouse and keyboard on 2015 iMac

Discussion in 'iMac' started by jennyp, Jun 20, 2018.

  1. jennyp macrumors 6502

    Oct 27, 2007
    I'm having freezing or lock-up issues with my iMac (Retina 5K, 27-inch, Late 2015). Its specs are: processor: 4 GHz Intel Core i7; memory: 32 GB 1867 MHz DDR3; graphics: AMD Radeon R9 M395X 4096 MB; storage: 1TB SSD (Apple) currently with 459 GB available; macOS installed: "High Sierra" 10.13.5 (17F77).

    The mouse is an Apple Bluetooth magic mouse. The keyboard is an extended Apple keyboard connected by a USB cable.

    What happens is that, without warning, the mouse and keyboard become frozen. I move the mouse but the screen cursor doesn't move. Then, after maybe 30 seconds or so (it varies), the cursor will suddenly be responsive again, but only to stop again seconds later. The keyboard is similarly unresponsive.

    When the freezes occur, the seconds on the menubar clock sometimes keep ticking, sometimes not, though it's hard to tell if that's during a freeze or not. If I'm playing audio, that will keep playing during a freeze.

    I have to wait for one of the "windows" of responsiveness to try to quit running apps, though this isn't always possible because they are so short. Often I'm just forced to shut down the iMac with the power button and restart.

    I never know when it's going to happen, though I get the impression (maybe not accurate) that it's more likely to happen after the iMac's been on for a few hours, rather than happening soon after a restart. It doesn't seem to happen when I'm doing any specific task or running any specific application.

    It's a significant problem because obviously I can lose work. Also, being random, it's kind of puts you on edge, wondering whether it's going to happen.

    I've reset the NVRAM and the SMC, but the problem continues.

    I'm keen to know if anyone else has experienced this problem, and whether it's likely to be a software or a hardware related issue.
  2. NajamQ macrumors member

    Apr 30, 2018
    Have you tried booting into safe mode?

    It will isolate the issue if OS is having problems. Use a USB mouse for time being.

    My iMac started to behave erratically about 2 years ago. Wasn't able to isolate the issue until the magic mouse battries died, I plugged in a USB wired mouse I had lying around. Suddenly the issue disappeared. Put new batteries in Magic Mouse and it started to happen again. So I just stopped using the MM and the issue never returned, even now I can replicate the same behavior if I use MM.

    Don't know if it helps you but it's worth trying a wired mouse to see if bluetooth interference is causing input to lock up.

    Other cause would be overheating. That i7 iMac is known to overheat. Although M395x is supposed to be cooler than M295x.
  3. wardie macrumors 6502

    Aug 18, 2008
    You sure it’s not “just” a Bluetooth dropout? I was getting these on keyboard and mouse on 2017 5k i7 iMac until I did a Bluetooth module reset (google it if needed)
  4. jennyp thread starter macrumors 6502

    Oct 27, 2007
    Thanks for the suggestions. Thing is it's also affecting the wired USB keyboard, so I don't see how it's a Bluetooth problem.

    I'll try the safe mode, but the problem is the intermittent nature. I'll have to use it in that mode for quite a while to see if that changes anything.

    I'm wondering if anyone else had had this affect both Bluetooth and wired USB peripheral devices.
  5. tubeexperience macrumors 68040

    Feb 17, 2016
  6. jennyp thread starter macrumors 6502

    Oct 27, 2007

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5 June 20, 2018