D5-300C humming noise

[ablats]

Hi, I've been using the TerraMaster D5-300C with 5 JBOD drives for about 3 years. In the last couple months, the DAS has frequently started making loud humming / vibration noises frequently, many times during the day for minutes at a time, even when the drives aren't being used at all by my computer. These vibration noises go away temporarily when I physically touch the enclosure.

A few questions:
1) Is this known / expected in any way? Could some fan part or something be responsible?
2) If I start pulling out drives from the DAS and replacing them one by one, possibly in different slots than before, to try to see if one of the drives is responsible, will that cause any issues? For example, would a drive be reformatted due to being removed and later inserted in a different slot in the DAS?
3) If I get a new D5-300C (same model) to replace the old one, can I simply move over the drives as-is? Or would doing so reformat them or cause other issues?
4) I've noticed that a couple times I disconnected and reconnected the DAS from my computer, the DAS spent a day or two making frequent hard drive noise (seek sounds even when I'm not using the drives) before quieting down again. Is the DAS doing something internally as a result of the disconnection? Such as, building a file index or something?

[TMroy]

Please try to remove the tray from the enclosure and insert it again to make sure the tray is well mounted.If you did any RAID Configuration for your hard drives? if not, you can directly buy a new model and just plug your drives in. if you have RAID configuration, you need to be careful to do that.

[TMRyan]

1) The two fans of the D5-300C will not make a lot of noise when the hard disk is not inserted and the two fans are turned on. After using it for 3 years, it is recommended that you clean the fan from dust. In addition, the HDD may cause humming/vibration noise. It is recommended that you check whether the HDD is installed loosely.
2) For D5-300C, HDD1/2 have RAID function, HDD3/4/5 are independent single disks. In non-RAID mode, the HDD is safely ejected and the device is shut down. It is a normal operation to replace the HDD again and will not cause a prompt to format. .
3) The same model of D5-300C does not need to be reformatted when replacing the HDD. It is recommended to replace the HDD when the device is turned off.
4) D5-300C is a simple hardware device, there is no application to make the HDD work, unless the PC is reading or scanning some files of the D5-300C HDD, it is recommended that you find a dataless HDD and try to install it.