3 sourced reports, with what to check before you buy. Each one links to the page it was reported on.
Worth checking
Creality publishes a USB 'brick recovery' flashing process for the K1 Max
Creality maintains an official 'brick rescue / line flashing' procedure for the K1 Max, which confirms that firmware-level bricking is a recognized failure mode requiring USB boot flashing to recover.
What to check. Firmware updates can brick the K1 Max to the point where it needs a USB boot-mode reflash. A buyer should keep the official recovery procedure and firmware image handy before updating, and be prepared for a non-trivial recovery if an update fails.
Extruder clogging and filament feed failure are documented failure modes on the K1 Max
Creality's own troubleshooting wiki lists clogging of the extruder front shell, the Teflon tube, the throat and the nozzle as the standard 'no filament out' failure modes, with a multi-step teardown to clear them.
What to check. A buyer should expect the extruder/hotend to clog and require disassembly (removing the extrusion kit, cleaning the drive gear, clearing the Teflon tube/throat) to clear. This is a documented, recurring maintenance task, not a one-off defect.
Firmware update changed nozzle-to-bed clearance, causing the nozzle to rub the textured plate
An owner reports that after updating to the latest K1 Max firmware the nozzle began rubbing the textured build plate despite leveling, and had to re-run full calibration. A second user hesitates to update, worried about bugs.
What to check. After a firmware update, the printer may lose correct nozzle-to-bed clearance and rub the plate; a full re-calibration after the update is the expected fix. Users should budget time for re-leveling after firmware changes.
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 3D printers catalog, version 0.1.1, under the CC-BY-SA-4.0 license.
