The POST and RMP variants have a dual-detector seeker: IR and UV. This allows it to distinguish targets from countermeasures much better than the Redeye and FIM-92A, which have IR-only. While modern flares can have an IR signature that is closely matched to the launching aircraft's engine exhaust, there is a readily distinguishable difference in UV signature between flares and jet engines.[4]

they're still updating the old tech with new trackers.

The original Stinger's reprogrammable microprocessor will become obsolete in 2023, and a service life extension will keep the Block I in service until 2030. With the arsenal declining from obsolescence, on 10 November 2020 the U.S. Army issued a request for information for a replacement MANPADS. The new system will be compatible with the Stinger Vehicle Universal Launcher used on the IM-SHORAD and be able to defeat fixed- and rotary-wing aircraft, as well as Group 2 and 3 UAS as well or better than the Stinger. A contract for up to 8,000 missiles is planned to be awarded by 2026.[5][6]