Please do NOT add images via the "attach files" box, as you are then forcing everyone to DOWNLOAD the file to view it outside their browser. Drag/drop the image files directly ONTO your reply box so other users can see them without needing to download unknown strange files. Thank you!
Please tell us your system specs: OS version, Premiere version, amount of RAM, Hardware specs including graphics card
and tell us your source properties and your sequence settings.
By any chance are you working with screen capture footage or material shot on a smart phone? If so, the problem is probably variable frame rate sources. Post back if that's the case and some one will elucidate further...