The NBA is investigating J.R. Smith’s latest faux pas — untying the shoelace of the Mavericks’ Shawn Marion while they awaited foul shots during Sunday night’s game, a league source said.

A decision should be reached Tuesday when interviews are completed. A source said no player has ever been disciplined for such a bizarre transgression. Smith spent Monday issuing dozens of tweets, responding to many angry fans.

Smith’s mischievousness is no longer being regarded as cute, or J.R. being J.R. by the organization. Especially when he’s not drilling big-time shots and averaging 18 points per game as he did last season. The sixth man with nine lives may be on No. 10. The NBA must determine whether this latest occurrence could have put Marion in danger.

The NBA has fined Smith twice for inappropriate Twitter messages and suspended him for failing three marijuana tests and elbowing Jason Terry, then with the Celtics, during last season’s playoffs. With Smith’s record, the NBA probably will not go easy.

Smith had a rough road trip in Texas. He got blamed for the Houston loss for taking an open 3-pointer with 22 seconds left in a tie game with the shot clock turned off. Smith claimed he thought the Knicks were down 2, which he may have thought was the lesser of two evils.