Here's one published by the US Department of Education's National Center for Education Statistics: "Children Who Enter Kindergarten Late Or Repeat Kindergarten: Their Characteristics And Later School Performance." It is available free online here.
This says behavior problems get worse for retained kindergarteners:
Children who had been required to spend two years in kindergarten performed significantly worse than their first- and second-grade classmates on all five of the 1993 indicators, and on two of the four 1995 indicators (table 2). In 1993, 40 percent of the retained pupils were said to have problems concentrating; more than a third, to be not learning up to their capabilities; and 29 percent, to be acting up or disrupting the class. All of these proportions were 40 to 50 percent higher than those for children who had not been retained in kindergarten. While less than a fifth of the retained pupils were said to have trouble taking turns or sharing with others, this proportion was twice as high as that for non-retained pupils.