my mira sports electric shower has shorted out x3, it's fixed about 300mm from the right return, told that the water may splash and enter the box, and need to move it further away to prevent splash.

Sounds more like the element is going, and its a neutral to earth fault causing teh RCD to trip?

all showers are designed to be fitted where water will be splashed on , has the shower been sealed around the outside where it meets the wall? this should not be done as any water running down the wall can collectinside the unit, regards Terry.