Assuming you've made no change in the model, nor in the Tersus version you're using, the culprit is probably the browser type or version (which has probably changed over the years), rather than the move from 32 to 64 bit Windows.
Try using your app in Incognito/InPrivate mode to rule out browser caching issues.
Also try debugging/tracing your app (see http://www.tersus.com/#Tag=Trace for more details).
Please let me know your findings,
For best results, use the Firefox browser..