If you place a comparator, power it (easier to see bug with a lower input), place one piece of redstone in front then another one next to that one (anywhere). After that power the second wire and the first wire will not update and all pieces of redstone connected to that will continue hte comparators power... if that makes sense?
14th duplicate of MC-5742, please use the search function to see if your bug has already been submitted. Currently over 42% of tickets are being closed as duplicate.