Early Bird Benefit - Bubble Protection - I bought staking off a player and I believe they intentionally tried to finish on the Bubble to avoid paying me, what can I do?

Staking and Bubble Protection are completely separate things, Bubble Protection is a free promotion for players who pre-register for tournaments and anything earned from the Bubble Protection promotion belongs to the player, it is not shared with backers

Plus, it is virtually impossible to attempt to finish on the bubble in a tournament deliberately as so many variables are beyond the control of players.