stop fuse 15a blowing on vivaro ?

my 2006 vauxhall vivaro has recently started blowing the 15a stop fuse shutting off the display unit in dash and killing indicators and brake lights. or if driving ur fine as will not cut off but once ignition is turned off the immob is on so wont start.the gaps between it blowing first time ans second was 4 months then 2 weeks now everyday or every other day as usual vauxhall dealer shutting me off ! has anybody else experieced this fault and what was it thanks!