Unfortunately, there will inevitably be some adjustment in dealing with the 40 second play clock in unexpected situations, and likely individual common sense will be the prevailing factor. Even with the former 25 second RFP, if some equipment malfunction could be corrected without assistance from the bench, or excessively delaying the RFP, we usually tried to correct the problem, without causing unnecessary (or excessive) delay without replacing the player WHEN POSSIBLE & PRACTICAL.
Common sense still will dictate which side of the line the specific situation calls for, (stopping play to allow a player to retie an open shoelace normally wouldn't require a substitution, however, if he broke the lace trying to retie it, he'd likely have to be replaced to safely correct the problem.)
Our 2019 Officials Manual still reminds us, in Basic Philosophy & Principles: "In addition to a complete mastery of the rules, game officials must have a good knowledge of human nature and the ability to control situations as they arise......At times the emotions of players, coaches and crowds run high and game officials must control themselves in order to provide leadership......Game officials must have a football sense which supersedes the technical application of the rules so that the game goes smoothly. Game officials are expected to exercise good judgment in applying the rules."