Startup Manager shows randomly on 2012 Mini

[tomdz]

Hi,
I have a strange issue with my 2012 Mini. Once in a few boots, usually every 1-2 days, instead of loading the system immediately, the Mini ends up in the startup manager. All partitions are there but I need to select the sys partition manually to continue. All works fine afterwards, no Startup Manager during the next boot up either.
I have tried resetting the NVRAM and SMC without success, the issue keeps returning.
The mini is running OS X 10.10.1 off a Samsung 850 Pro SSD.
Any ideas?

 

[Celerondon]

Keyboard Problem?

...Once in a few boots, usually every 1-2 days, instead of loading the system immediately, the Mini ends up in the startup manager...

A sticking Option key could cause this problem. You could try another keyboard to eliminate or identify the keyboard as the source.

 

[tomdz]

Thanks for your reply, Celerondon.

I don't really have an extra keyboard to verify, but the Apple Wireless I own is new (just as the Mac Mini), batteries are ok and there are absolutely no issues with the keyboard in regular use.

I actually thought that 10.10.2 had resolved the problem cause since updating on day one I had not seen it once. Until today...

When it happens, instead of the Apple splash being shown almost immediately, a white screen is visible for quite a few seconds. Then the Startup Manager comes up with all the drives available.

 

[redheeler]

Thanks for your reply, Celerondon.

I don't really have an extra keyboard to verify, but the Apple Wireless I own is new (just as the Mac Mini), batteries are ok and there are absolutely no issues with the keyboard in regular use.

I actually thought that 10.10.2 had resolved the problem cause since updating on day one I had not seen it once. Until today...

When it happens, instead of the Apple splash being shown almost immediately, a white screen is visible for quite a few seconds. Then the Startup Manager comes up with all the drives available.

A sticky Option key should also cause some abnormal behavior while in the OS. How often does the boot menu appear, every boot or just occasionally?

 

[tomdz]

It's occasional.

I used to see it every 1-2 days when I had two HDD enclosures connected to USB ports. Then I unplugged the drives at the other end, leaving the hanging cords still connected to the Mac but there was no significant change. I thought things had improved though once I disconnected the USB cables altogether - I had not seen the problem for a couple of days.

Then I installed 10.10.2, did not reproduce the issue for a while and since the update actually fixed another annoying bug (audio balance becoming off after each boot) I decided to give it a try and connected everything back. For another few days everything was just fine. Until today...