Frequent hard drive WD Red 4TB failures

Hi all, I bought a ReadyNAS (104) in 2016, and I equipped it with 4 hd WD red 4 TB (X-Raid). Since 2016 I had to replace disks almosts once a year: during the first year I had to replace one disk, during 2018 I had to replce two disks, and yesterday I had another disk failure, so now I had to buy another one. I'm not an advnaced user or an expert on NAS usage, but I guess these failures are too frequent. I have some external disk which have 5 or more years, so it is very strange that WD red disks would broke so frequently.

Any idea on what is going on?

In the last log I extract from ready nas I read the message " ****************************************************************************
Caution: Found protective or hybrid MBR and corrupt GPT. Using GPT, but disk
verification and recovery are STRONGLY recommended.
****************************************************************************"

Thanks in advance for any hint.

Daniele