Forms should be expected to be quick and responsive for users. When you experience any slowness in an output form, the first place to check is whether the output form as the "On Display Detail" event enabled as this event is triggered for every record and object displayed in the form. When something as simple as scrolling through the records, this event can be triggered a numerous amount of times.

To narrow down the issue:

1. Uncheck the "On Display Detail" event and test whether lag persists
2. If that event is the culprit, check what code is running and see whether the code can be modified, reduced, or omitted to save performance.