According to those who have worked with the elder Willis on his recent films, the actor has been exhibiting signs of decline in recent years. In interviews with The Times this month, nearly two dozen people who were on set with the actor expressed concern about Willis’ well-being.

These individuals questioned whether the actor was fully aware of his surroundings on set, where he was often paid $2 million for two days of work, according to documents viewed by The Times. Filmmakers described heart-wrenching scenes as the beloved “Pulp Fiction” star grappled with his loss of mental acuity and an inability to remember his dialogue. An actor who traveled with Willis would feed the star his lines through an earpiece, known in the industry as an “earwig,” according to several sources. Most action scenes, particularly those that involved choreographed gunfire, were filmed using a body double as a substitute for Willis.

In one alleged incident two years ago on a Cincinnati set of the movie “Hard Kill,” Willis unexpectedly fired a gun loaded with a blank on the wrong cue, according to two people familiar with the incident who were not authorized to comment. No one was injured. The film’s producer disputed that the incident occurred, but the alleged discharge left actors and crew members shaken.