Likely causes of right trigger failing to reset?

[OH Osthaus]

removing the floor plate would let you know if it is dirt just in the trigger,

following Brian's disassembling instructions for the action may give you a clearer picture

[Scott Gentry]

Had a 1891 GH do the same thing last week, pulled trigger and cleaned with solvent and good as new. Wasn't that much dirt, just stiff crud that hindered movement.

Good luck.