Dory, here's one:
Start Advanced FireCalc.
Input 55,000 for spending, check the optional 95% rule. Leave everything else at their default value. Click Submit.
Look at the charts: The withdrawals chart is in the positive side all the time (as expected). The portfolio value chart has negative values starting around 1918 and ending around 1930. The two charts contradict each other.
But here's the fun part: Save this result (Link to this set of data). Close all browers. Open a new browser, and paste the saved link. Click submit, and you should get a totally different result that makes more sense. Both graphs are positive.