Swapping mach & speed modes on descent causes speed to overflow into -2147483648

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As title implies, pressing the "MACH SPEED" button on the MCP will increase the speed to unreasonably high amounts, first to some high value, then another even higher value, finally overflowing into -2147483648, at which point it stops increasing / decreasing

From there, the only solution is to set managed and then go back to selected

Autosave file included. To reproduce, load autosave, click mach speed button a bunch, and observe the bug

SPEEDBUG.bin