MySQL:esta versión de MySQL aún no es compatible con la subconsulta 'LIMIT &IN/ALL/ANY/SOME'

En lugar de usar IN, puede usar JOIN

SELECT v.VID, v.thumb
FROM video AS v
INNER JOIN
     (SELECT VID
     FROM video
     WHERE title LIKE "%'.$Channel['name'].'%"
     ORDER BY viewtime DESC
     LIMIT 5) as v2
  ON v.VID = v2.VID
ORDER BY RAND()
LIMIT 1