AWS EC2 t2.micro instance very unstable

I'm running a wordpress page on an AWS EC2 t2.micro instance. Nothing fancy but just a simple wordpress site.

It has been happening pretty consistently that every few weeks:

1. my page will be unreachable, ssh not reachable either
2. when check on dashboard, everything looks right, no warning or complaints
3. reboot it on AWS admin panel, one of the check will fail: "Instance reachability check failed at (time) "

System log shows that there's a kernel panic (all log copied below). What could cause this? bad hardware at AWS side? This really puzzles me a lot, please help. Thanks!

[2950123.794183] end_request: I/O error, dev xvda, sector 13514688
[2950123.797618] end_request: I/O error, dev xvda, sector 13514712
[2950123.798170] end_request: I/O error, dev xvda, sector 13514776
[2950123.798170] end_request: I/O error, dev xvda, sector 13514816
[2950123.798170] end_request: I/O error, dev xvda, sector 13514872
[2950123.798170] end_request: I/O error, dev xvda, sector 12894512
[2950123.798170] end_request: I/O error, dev xvda, sector 12875536
[2950123.798170] end_request: I/O error, dev xvda, sector 511456
[2950123.798170] end_request: I/O error, dev xvda, sector 13403944
[2950123.798170] end_request: I/O error, dev xvda, sector 515968
[2950124.114201] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000007
[2950124.114201] 
[2950124.118093] CPU: 0 PID: 1 Comm: init Not tainted 3.14.35-28.38.amzn1.x86_64 #1
[2950124.118093] Hardware name: Xen HVM domU, BIOS 4.2.amazon 05/06/2015
[2950124.118093]  ffff88003d578ae0 ffff88003da2bc80 ffffffff814867ca ffffffff81788cf0
[2950124.118093]  ffff88003da2bcf8 ffffffff814825ab ffffffff00000010 ffff88003da2bd08
[2950124.118093]  ffff88003da2bca8 ffffffff81c9af20 0000000000000007 ffff88003da30480
[2950124.118093] Call Trace:
[2950124.118093]  [<ffffffff814867ca>] dump_stack+0x45/0x56
[2950124.118093]  [<ffffffff814825ab>] panic+0xc8/0x1cd
[2950124.118093]  [<ffffffff8105ffd1>] do_exit+0xa41/0xa50
[2950124.118093]  [<ffffffff8106005f>] do_group_exit+0x3f/0xa0
[2950124.118093]  [<ffffffff8106f707>] get_signal_to_deliver+0x1c7/0x6e0
[2950124.118093]  [<ffffffff81014458>] do_signal+0x48/0x6f0
[2950124.118093]  [<ffffffff811e7c38>] ? fsnotify+0x228/0x2f0
[2950124.118093]  [<ffffffff81014b68>] do_notify_resume+0x68/0x90
[2950124.118093]  [<ffffffff8148d822>] retint_signal+0x48/0x86