Currently, when an Unstable Meltdown alert is triggered, the continent stays in a fully opened state for the 45 minute duration. There were no patch notes that specified a change in this category. This bug seemingly appeared after the September 7th, 2022 Update. Perhaps the Sudden Death alert changes broke something? For reference, Indar is supposed to use the following lattice layout if an Unstable Meltdown alert is triggered: Esamir, Amerish, and Hossin also had their own versions of the Unstable Meltdown lattice layout.
Providing 2 screenshots of the currently-bugged 'Unstable Meltdown alert', taken today on the Connery server around 5:08 AM Pacific Standard. The first one shows that we are supposedly having an 'Unstable Meltdown' alert: And the second one shows that we currently do not have the reduced lattice that an Unstable Meltdown alert is normally supposed to trigger, despite having the reduced alert duration as expected: