Thanks for your interesting the QRTEngine!
1) Does the jolting persist if you run the survey without preview mode on? Ie, launch the survey and then run it. The preview mode box at the top is what causes the jolting, usually.
2) What usually causes the freezing is a slow connection to the Qualtrics server. A good way to check whether this is actually the case is by analyzing the data file (run it through the parser). If done correctly, you’ll see a InitPre[CalculatedDuration] column. This column tells you how long it took, in milliseconds, to load the page. If high values in this column (>1500-2000) correspond to freezes of the survey, the loading time is your culprit. If it’s not, let us know!
Hopefully this helps.