Replace HDD in EX4100 RAID5 with larger drive?

My Cloud OS 5 My Cloud EX
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I’ve seen two different answers to this question so I’d like to know the correct procedure.
My EX4100 is populated with 4 x 4TB drives, only one of which was new when I built out the box. (Don’t ask about the others. I will say the QC number on one of them is CCXI.)
As I’m in the process of digitizing about 40+ years of photographs and a couple hundred CDs/DVDs, I’m going to soon run out of capacity. One article said one can only swap like size drives, that is, replace a 4TB drive with another 4TB. A thread on this forum said there’s a page that explains how to swap HDD with a larger one.
So, which is it? Or do I need to buy a whole new NAS box?

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Hi @GleasonFan,

Have you opened a Support Case? If not opened, for more information, please contact the WD Technical Support team for the best assistance and troubleshooting:
https://support-en.wd.com/app/ask

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I’m still waiting for WD Support to respond to a request made in March.

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Still no replies.