Nook HD+ hardware diagnostic?

[asenr]

Hi guys,

I have a Nook HD+ running cm-11-20141112-SNAPSHOT-M12-ovation for a long time with no problems but yesterday something happened and now it boots very slow and keeps restarting after bootup animation. I did factory reset, tried reinstalling cm-11-20141112-SNAPSHOT-M12-ovation or installing the latest nightly build, but nothing helped. So I suppose it's a hardware problem, most probably with RAM or ROM, but how can I check it for sure? Is there any way to run some diagnostic software? Any help is much appreciated

 

[asenr]

Whatever I do - deleting files and directories in adb shell, formatting partitions, flashing ROMs and recovery images... it says: ok, completed successfully, and then I mount the filesystem and it's all there - my cm-11-20141112-SNAPSHOT-M12, CWM v6.0.4.6, even all the user profiles and data. I can't delete a single file. Is there any software protection that causes such a behavior or it's a hardware fault? IMO some memory circuit needs replacement but I'm a hardware guy, new to Android and CM and I may be missing some stupid detail