I have three fixes:
1) Every couple of months remove the battery and scrap the gold gold contacts to remove any tarnish, the gold contacts of the Sensation have pinpoint contacts. (This may be why Apple solder their batteries in)
2) Pack the bottom edge with a thin piece of card (a cut up train ticket works well) to make the battery a really tight fit.
3) Dump the stock HTC battery and buy an Anker battery, about £8 on Amazon and offering considerably better performance than the original battery.
Hard to believe such amazing technology could suffer such silly faults……