What happens when a tag is bent?

Three outcomes

A gentle curve is fine. A flexible label wrapped around a bottle or a cable keeps its antenna continuous and its chip bond intact. Tags are sold for exactly this.

A crease kills. Folding a tag sharply breaks the conductor where the fold crosses it. The loop is open, no current flows, and the tag is inert with nothing visible from outside.

Repeated flexing fatigues. The bond between chip and antenna is small and stiff, and working it hundreds of times weakens it. This is the failure mode of a card in a back pocket.

The intermittent case is the worst

A fatigued bond does not fail cleanly. It makes contact sometimes, so the tag reads at very close range, or on one phone and not another, or after several attempts.

That behaviour survives testing, because a tester who gets a read moves on. It then fails for a customer, who reports the tag as unreliable rather than broken.

It also invites the wrong diagnosis. The symptoms look like a range problem, a phone problem or a surface problem, and people spend a long time on those before suspecting the tag.

Any tag that reads inconsistently at close range, having previously worked, should be treated as mechanically damaged rather than investigated further.

Diagnosing a bent tag

Compare with an identical tag that has not been bent. If the new one reads normally in the same position on the same phone, the old one is damaged.

Try several phones. A tag that reads on one device and nothing else is usually failing rather than incompatible, since compatibility does not change with time.

Look at the tag against a light if it is a thin label. A crease across the antenna is sometimes visible as a line in the foil.

And do not spend long on it. A tag is a few cents, the diagnosis is worth minutes not hours, and replacement is the fix in every case.

Choosing tags that tolerate it

Flexible labels on PET for anything curved or wrapped, since they are built to bend and stay bent.

Rigid encapsulation for anything that will be handled and pocketed, because rigidity protects the antenna by refusing to move.

Avoid the middle ground of a semi rigid card that will be flexed daily. It is stiff enough to concentrate stress at the chip and flexible enough to keep doing it.

And where a tag must be both thin and handled, expect a finite life and plan replacement rather than treating a failure as a surprise.