Version 8.8 should be stable, so two things come to mind:
1. Perhaps you do have a hard drive failing intermittently. Although I would think the software should tell you the hard drive is offline or failing. I would check the SATA and power connections are secure.
2. The array sometimes rebuilds when the computer didn't shut off or reboot correctly. I've never seen the software just start rebuilding randomly.
I would check the hard drive SMART data and do a hard drive test to make sure one of your drives isn't failing.
The rebuild times are also significantly faster in the new rapid storage driver. But really you shouldn't be rebuilding for no reason.
Thank you hechacker1.
I followed your steps and opened up my PC case to check all the SATA cables. I couldn't find anything wrong, and all the SATA connectors were plugged in. I did notice though that my PC case door was putting pressure on the SATA connectors as there were no space to breathe between the HDD and the PC case door. I managed to give them a little bit more space, and after this the raid haven't been rebuilding. So problem solved Thanks!