Raid10 - plug-out disk and Raid10 inactive

[geniety_alex]

Hi there,
I got this problem:
one disk got I/O error info after scan and still got "bad block". so, i deciced to Hot-swap disk. follow this step:
1. before I plug out disk, this disk was corrected by Nas, info show like this:
Host: Drive2 read error corrected.

2. I still decide to plug out this disk, then, after I plug out this disk for few seconds, info show:
[RAID10 Disk Volume: Drive 16 2 3 4 5 6 1 8] Drive 2 removed.

3. we has an Global spare disk on NAS, so the normal way is that after this disk plug out, Global spare disk will join to Raid10 and rebuild, but:
[RAID10 Disk Volume: Drive 16 2 3 4 5 6 1 8] RAID device is inactive.

4. I wait for 10mins, the status no any change, so I had to reboot Nas.

5. After NAS root, Raid10 actived and Global spare disk rebuild proper!!!

My question is why this happen?

we get another disk error this week, the disk is belong to Raid10:

[Drive 1] Bad Blocks Scan completed. 8 bad block(s) found.
[Harddisk 1] medium error. Please run bad block scan on this drive or replace the drive if the error persists.
[Harddisk 1] I/O error, sense_key=0x3, asc=0x11, ascq=0x4, CDB=28 00 5d 18 c9 00 00 00 80 00 .

How should I do to hotswap this disk this time? (Global spare is ready)

so, anybody help!
thx!

[geniety_alex]

Additional:
Raid10 inactive already happen last year when plug out error disk (turely error found) and host-swap disk with global spare disk.
we rebooted NAS last year still..... then disk rebuild with good.
so weired!