Mr. Monk and Little Monk - S4-E8
Continuity mistake: When Monk is doing the summation for the present-day case with Sherry's ex-husband sitting in the chair, at first you can see that the painting is directly behind him. However, shortly thereafter during the summation, the painting has somehow shifted to the viewer's left and is no longer directly behind him. While it's plausible that someone could have moved the painting, it's just not believable since less than a minute has passed. Besides, would Lt. Disher (he was closest) really take it upon himself to move evidence?