You could use the magnets is a primary way to hold the door open and then put two brass rings or hooks 2/3 of the way up on each side of the door on the trailer and a bungee across it as a secondary safety.
2022 RAM 3500 DRW, 4X4, 4.10, 6.4 Hemi, 50 Gal Gas, Curt A20 hitch, Tire Minder
Traded: 2018 RAM 3500 DRW, 4X4, 4.10, 6.4 Hemi, Curt A20 hitch, Tire Minder
2018 North Point 315rlts with most of the options.
Dish Hopper With 2 Joeys & Birdog Meter, 2-2K Champion Generators