Any "loose earth" connection should be made good i.e. tightened - not removed completely which would be unsafe and probably illegal - and an earth connection is very unlikely to work itself loose.
From reading this ...
http://www.diynot.com/forums/viewtopic.php?t=6852
It seems to me your WM motor is tripping the RCBO only when on high load and therefore highest current. It follows then that your RCBO is tripping because of overload curent.
Perhaps you need an RCBO with a higher threshold of Overload current? Or an RCD instead. Your WM has been working fine for some time - the problem arrived with the RCBO. Your installer may have selected an inappropriate protection device.
Peccavi
October 2008