Backrest won't stay up / keeps dropping

What's actually wrong

Here's the twist: on ratchet-back chairs, a back that keeps dropping usually is NOT broken. Raising the back past its top notch intentionally releases the ratchet so it drops to the bottom for repositioning — people then raise it all the way again and repeat the cycle forever. The fix is free: reset, then stop one notch below the top. Actual failures (worn mechanism, sheared bolts, cracked attachments) are the minority case.

Symptoms

• Backrest slides or clunks down while sitting
• Back drops to the bottom after being raised to its highest position
• Lumbar support loose or rattling

The fix, step by step

1. The ratchet reset: firmly lift the backrest all the way to the top — the mechanism releases and the back drops to its lowest position. That's by design
2. Now raise it slowly, click by click, and STOP one notch below the maximum. It will hold
3. If it still slips at middle positions, check and tighten the bolts joining the backrest to the seat mechanism (behind a plastic cover on most chairs)
4. Inspect for cracked plastic at the attachment — structural cracks are not repairable safely

When to skip DIY

Structural failure on any chair you'd sit in daily — replace the part via manufacturer, or replace the chair on budget models. A cracked back support is a real injury risk.