If you have horizontal aluminum siding, then like other types of 'lap siding', each strip is attached along its top edge to the wood substrate with staples. They are stapled in between the studs. If the staples are too long or air pressure was too high, then the tips of the staples could penetrate thru the interior paneling as well and create the bumps you feel. And since the staples are not galvanized, humidity inside the trailer will cause the tips to rust.
Texas Baptist Men-Retiree Builders member since '01
13 Silverado 3500HD D/A, 2wd CCSB srw, custom RKI bed
11 Cruiser CF32MK