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Isolation is your friend. Ignore strumming and concentrate on just your fretting hand. Slowly finger the chord, put your hand on your knee and repeat forming the chord. After a few minutes of this exercise, add a single strum after you have placed your fingers. Then pick each string and reposition your fingers to eliminate any buzzing or muted notes. Do this all slowly. Finally add the metronome as described above.
Most chord transition challenges come about because you have not engrained the shape in your brain. The above exercise will help.
When you move on to transitions go back to slowly switching back and forth between the 2 chords.
Above all be patient. I have had a couple chord transitions that have taken me months to master