Linkage issue

[welfordnremt]

Hey guys,
I need a little help. First of all I am not very mechanically inclined so bear with me. About every two weeks the plastic clip that holds the linkage rod to the bar on the side of the transmission pops off. All I have to do is push the plastic clip back on the bar and I am good for another two weeks or so. Any ideas why this is happening or what I need to do to fix it?

Everything lines up on the column D=D and R=R so the adjustment seems right.

It is a 2003 F-250 6.0 KR.

Thanks