I'm almost positive this issue has nothing to do w being jailbroken, it's existed in varying degrees since iOS 6 launched, well before a JB was written for it.Then I guess your only choice is to just deal with the problem.
Since you're jailbroken, is there a way to manually edit the dictionary? Maybe there are words that it remembers that are causing this issue. You should post a thread in the JB section or have this one moved.
