A long time ago, I posted about similar problems when I try to make line charts of combination symbols covering intervals of 2 to 4 hours or less. The problem would not occur when I tried to chart full day intervals, or when I tried to chart the individual legs of these combinations. They couldn't reproduce the problem. They eventually stated that all these types of problems with charts would be resolved by updating to TWS version 853. I never updated to that version, because I am seeing too many dangerous problems. I am still monitoring the bboards and looking for indications that it is safe to update. I just recently saw a posting saying that version 853 is, at least temporarily, no longer available on the IB website, so this was a hint to me that it is not yet safe to update. So I am in limbo, for a very long time, waiting to see if TWS 853 will solve my charting problems.