Nucleo F401 only works right after flashing, not after power cycle

Log from incident, this was the first time I was able to connect and get more than just the > after flashing several times, and trying to connect without powercycling:

Connected
>I˅lInvalid saved code in flash!
>
=undefined
>  //Oh hey, it's not non-responsive. Better reset() and save()!
=undefined
>reset()
=undefined
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>save()
=undefined
Erasing Flash...
Writing.....
Compressed 86016 bytes to 2657
Checking...
Done!
>
=undefined
>  //great, I'll disconnect, unplug+replug it, and reconnect.... 
Disconnected
Connected
> //and now this is all I see, typing has no effect. 
Disconnected
Connected
>

Any ideas?