4 sourced reports, with what to check before you buy. Each one links to the page it was reported on.
Costly or dangerous
Duo Plus series lid locking assembly can open under pressure, causing second/third-degree burns (US class action)
A Canadian consumer-law firm's investigation names the Duo Plus series among Instant Pot models covered by an ongoing US class action alleging a dangerously defective lid locking device that lets the lid open while contents are under pressure, ejecting superheated contents and burning users to the second and third degree. The page also states Instant Brands designed a new locking pin construction around 26 October 2017 to address the problem, so units built before that date are the ones in question.
What to check. If you are buying a Duo Plus in Turkey, this is the highest-risk finding: it alleges a lid-lock defect that can cause scalding burns under normal use. Prefer a unit manufactured after late 2017 (the page says the new locking-pin construction was designed around 26 October 2017), and treat any lid that opens while pressure is still inside as a serious hazard.
Error codes C1/C2/C6/C6H/C6L signal faulty temperature or pressure sensors; NoPr signal means the heating element has failed
The manufacturer's official troubleshooting sheet for the Duo Plus (and other series) lists error codes C1, C2, C6, C6H and C6L as faulty temperature/pressure sensors, and the NoPr code as a failed heating element — all requiring contacting Customer Care rather than a user fix. These are documented electrical-component failures specific to this model line.
What to check. If the display shows C1/C2/C6/C6H/C6L or NoPr, the unit has a failed sensor or heating element and the manual directs you to service, not a DIY repair. This is a reliability risk to weigh for a purchase, since these are internal parts not user-replaceable.
Steam leaks from side of lid when the sealing ring is damaged, not installed properly, or the ring rack is warped
The manufacturer's own Duo Plus troubleshooting manual lists steam leaking from the side of the lid as a documented fault, with causes including a damaged or mis-installed sealing ring, food debris on the ring, and a warped or off-centre sealing ring rack (which the manual says requires contacting Customer Care). This is the official failure mode behind the 'lid won't seal' complaint.
What to check. Steam escaping around the lid is the most common sealing failure on this model. It is usually the silicone sealing ring (a consumable that wears and absorbs odours) or a warped ring rack; the manual says a deformed rack means contacting service rather than a DIY fix. Budget for replacing the sealing ring over time.
Owner reports the lid cannot be made to seal due to the silicone O-ring design
A critical Amazon/Woot review of the Duo Plus (8-quart) reports being unable to get the lid to seal at all, blaming the large red O-ring and a lid that is hard to push down and turn to lock. This is a single owner's account of the same sealing failure the manual documents, but it is anecdotal and the reviewer could not get past a test run.
What to check. This is weaker evidence (one owner) but matches the official steam-leak troubleshooting. If you buy a Duo Plus, expect the sealing ring to need correct seating; test the seal with a water run before relying on it.
These reports come from the pages linked under each item: owner forums, repair guides and workshops. They are not a diagnosis of any one unit, and a careful check of the one you are buying still applies.
Text from the Kriko Instant Pot electric pressure cookers catalog, version 0.1.1, under the CC-BY-SA-4.0 license.
