whats up with my copy and past? It will just stop copy and pasting randomly and its not a dodgy keyboard. BuG?

say i animated and arm waving, If I copy the first frame on the full hand peg (selecting all pegs).

I should be able to move along to the next frame and Ctrl Past making the animation hold the pose like previous frame.

THIS WORKS YAY… lets move along the fames and do the same. at some point it just stops pasting???

Ill deselect the masterpeg and start again and “oh what the hell” it pastes fine? its not a dog keyboard.

spooky bug or am i missing something, its crazy annoying for me as a cutout artist.

can someone relate?