05AB1E, 14 bytes

[DγεDgÉ£}˜DŠQ#

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05AB1E, 13 bytes

[DγʒgÉ}€нDŠQ#

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Explanation:

[DγʒgÉ}€нDŠQ# Implicit input
[             Start infinite loop
 D            Duplicate
  γ           Split into chunks of equal elements
   ʒ  }       Filter by
    g           Length
     É          Odd? (0=falsy 1=truthy)
       €      Foreach command
        н     Head
         D    Duplicate
          Š   Push c, a, b
           Q  Equal? (0=falsy 1=truthy)
            # Break if true (i.e. equal to 1)