First-print cap fits, but the crown swims around in the disc hole. Three small tweaks, all on the cap (chassis hole stays at 16 mm): - Crown 15.0 → 15.7 mm — drops the radial clearance from 0.5 mm to 0.15 mm. Snug PLA-on-PLA sliding fit in the disc hole, no rattle. - Crown 6 → 8 mm tall — taller press target, 4 mm visible above the disc (was 2 mm). Hole engagement stays at the rim's 4 mm. - Plunger 5.5 → 6.5 mm — bumps plunger_preload from 2.3 to 3.3 mm, pushing the tapered tip deeper into the Atom button cap. The tapered side wall + tighter crown together resist cap tilt.