The reason for this misbehavior is, that the slide touch handler operates with the time when the event is handled and not with the time when the event occurs. Thus, the speed calculation is incorrect, when several touch events are queued.
We solved this problem within Embedded Wizard version V6.50. To be more precise, this is an enhancement of the Mosaic class library, where you will have the possibility to add a time stamp for each touch event. The new method SetUserInputTimestamp() can be called from the main loop every time before the touch event is inserted into the Embedded Wizard UI application.
What you need to ensure is, that you put the exact time stamp in milliseonds together with the touch coordinates within your message queue. When the event is later processed by the main loop, the exact timestamp (when the touch event occured) can be inserted into the Embedded Wizard UI application in order to calculate the appropriate scroll speeds.