2012 MacBook Pro crashing multiple times a day

[Grey-frog]

I have a 2012 MacBook Pro that is crashing multiple times a day. The screen flickers with weird boxes that seemingly show smaller versions of segments of other active windows. The flickering part happens all the time and doesn't seem to cause any problems other than that, but I'm sure it's not unrelated as both issues started around the same time. I do have a dual monitor setup and the flickering happens on both monitors. The mac does seem to crash more often if I'm watching videos in a browser such as on Youtube. My browser is Firefox, 42.0 and is up to date, if that helps.

I'm running on OS X El Capitan, Version 10.11.1. I have 413GBs of 500 free and 8GBs of RAM that I don't think is being taxed.

I've tried looking up a few solutions: and tried things such as OnyX and AVG AntiVirus but they haven't seemed to help. Any ideas?

I do have the error report from the most recent crash, but can't copy it into here because of the character limit.

 

[honestone]

Have you tried using Disk Utility to 1) Verify and Repair the Volume (ie, top level) and 2) Verify and Repair all visible partitions (ie, second level)? In order to do that, either you need to have an external backup made with something like SuperDuper!, or if you only use Time machine, then you can boot to the Recovery Partition and run Disk Utility from there. This link talks about that partition:

https://support.apple.com/en-us/HT201314

Hopefully, Disk Utility will be good enough. You might, though, want to consider investing in a more robust disk maintenance/repair utility. I myself have both TechTool Pro and Disk Warrior. I use TechTool Pro each week for both of my machines to perform quite a few disk maintenance and repair tasks (fortunately, repairs are just about non-existent). Like you, I also use Onyx (I assume you used the version specifically for El Capitan; a newer version, 3.1.2, came out earlier this week. You can get it from here: http://www.titanium.free.fr/onyx.html) as another part of those tasks.