OP is looking for backward-adjustment, Rolling over / continuous contracts are a different concept than backward adjustments. Looks to me (though I do not use Esignal) as if Esignal does not provide backward adjustment features. OP, one solution (though dirty) I could think of is to create a custom contract (your own) and code a formula that backward adjusts based on the roll over dates, but I am afraid it would entail lots of manual manipulation and maintenance (you would need to hard code the roll over dates [or you could automatically backward adjust gaps > x%, though it can be dangerous for contracts that might "lock" for several sessions and hence show large gaps once the contract is regularly trading again]).
The web site link shows a tick box: Back adjust previous data on rollover: Controls whether historical data is back adjusted when the contract rolls over to the new front month or not. Maybe OP just missed it?
I don't have time right now to check what's wrong but from what I can see on your chart, the symbol doesn't appear to include the months following the 'B' which may be the cause of your problem. You might want to check out the KnowledgeBase. http://kb.esignal.com/display/2/index.aspx?c=&cpc=&cid=&cat=&catURL=&r=0.685701608657837 Search 'back adjustment' > the 2nd entry, 78%......
Apologies, I just saw it too, after you pointed to it. Yes, seems there is a backward adjustment feature then...