East-West vulnerable at matchpoints. ACBL sectional pairs.
South is somewhat inexperienced (non-LM) and accustomed to limited games. North is a pickup partner. East-West are more experienced and in an established partnership.
East's 4♣ call was alerted. At his turn to call after 5♣, North inquired about the alert of 4♣. West first explained it as Non-Leaping Michaels and further specified it as showing clubs and a major.
After passes by North and East, South bid 5♦. At this point, West called the director, claiming that North broke tempo after the explanation. North confirmed that he had asked about the alert, but disputed that there was a pause afterward. The director then instructed the players to proceed and left the table. West then doubled, which was followed by three passes.
West led a club, and the table result was 5♦X=, NS +550.
How would you rule? Thanks in advance.