Pulsecoil immersion

Right I hope someone can help here as I'm at my wits end with this boiler.
Pulsecoil 2000.
I have replaced the boost immersion twice in 4 months the last one was absolutely cooked! I could only describe it as a catastrophic faiilure. Distorted and split after only 2 months. It is in a new apartment that is only 6 years old. The flat is tenanted and I'm in danger of losing my tenants over this re occurring problem.
I replaced the immersions with a standard off the shelf incoloy 2kw immersion. I noticed that the element is much shorter that the gledhill equivalent.
Are these parts from Screwfix & Toolstation inferior quality to gledhill and is this my problem.? I am amazed that a part can fail so quickly. I am assuming something else is causing it to fail so quickly as the OE parts have lasted 6 years.
My tenants have call again tonight to say they have no hot water again!!!!

I patiently await you advice.

Use the correct parts.
Mike

You should be using a 3KW element not a 2KW. You can get the right one via this link: Gledhill Pulsacoil 2000 Spares

Make sure you have also replaced the thermostat rod for the right one, the part number for that is XB081

I would personally just call a professional in who can sort the problem out straight away.