Q: Delayed Boot chime(bong) + Unable to boot.

Hi everyone,

On my MacBook Air 13'' (early 2015),

Every time I press the power button it takes about 20 to 25 seconds till I hear the boot chime after that it starts up normally till the apple boot logo but the progress bar gets stuck at about 75%. And it won't get past this point.

Tried SMC reset and Pram reset but no luck.

I tried booting with Linux (Ubuntu live USB) it works normally.

And if I just type reboot at Grub prompt and let it boot normally Mac OS magically starts as if nothing had happend .

But still if left in sleep for more than 3 hours it crashes and has to be forced shut down.

And again started up by using above method.

I have absolutely no idea what this is all about, but probably it´s something with the firmware (which is the most recent version on my machine)?

Any help would be appreciated.