WD15EARS-00Z5B1 Parition table lost and files start dissapearing?

I have this drive for about 4 months, but the performance is really awful I get about 10Mb/sec. I’m using Windows 7 and I have manually aligned the partitions in Linux using cfdisk.

Twice the drive was suddenly empty, the partition table was gone and I could restore it using testdisk in Linux.

Yesterday the drive was not found when waking from sleep and the free space had gone up from 10Gb to 150Gb, I don’t which files are missing.

Is there a firmware update for this disk and should I go for a RMA?