UK Bathroom/bedroom lighting issues

[WrightD14]

Hi, Just looking for some advice. In a bedroom there are 5 downlights on a dimmer switch. When turned on, every now and again these lights can sometimes go off when the light switch for the bathroom is turned on. There are 4 down lights in the bathroom just on a 2 way switch. Can any one cast any light on why this would be happening? They are on the same circuit but the but no physical switching wires between the bathroom and bedroom.
TIA

 

[Markyd]

could be a loose neutral at a junction box or switch

 

[suffolkspark]

Possibly feed out is loose in the bathroom switch on its way to the bedroom. Need to dismantle and check really