reflekti

The best false seam in the band, because both halves of it are alive and it is still false.

Re- is a fully productive Esperanto prefix meaning again or back: revidi to see again, redoni to give back, reveni to come back. And flekti is a real Esperanto verb meaning to bend, sitting just outside the course's first 3,000 roots. So re- plus flekti is a grammatical, buildable Esperanto word. It means to bend something back again. It does not mean to reflect.

Reflekti arrived as one borrowed root, reflekt-, and the meaning it carries is the optical and figurative one that Latin reflectere had already specialised into by the time European languages picked it up. You cannot assemble it from the parts and get there, which is the test that matters: a seam is real in Esperanto only if building from the pieces produces the attested meaning. Here it does not, so the root is atomic and you learn it whole.

And then the payoff, the same one neglekti and inspiri offer: the Latin behind it really is re- plus flectere, bend back. The intuition is historically correct and synchronically useless, and knowing which of those two you are relying on is a large part of not guessing wrong.

The native alternative. For the mirror sense Esperanto also has respeguli, built transparently from spegulo at rank 1165: to mirror something. It is the more Esperanto-ish choice and it is common. Reflekti keeps the physics (reflekti radiojn) and the figurative reporting sense in the third example; and note that for the English "to reflect on something", to think it over, neither word will do. That is pripensi.