timers crash in a loop with vibra and no sleep

When running (1.3 firmware i get a reproducible crash/hang with:

>>> while True:
...   vibra.vibrate(500)
...
MXC_ASSERT ../lib/FreeRTOS/Source/timers.c #386: (xTimer)

After that, the repl doesn't respond to any input, and the vibration get executed just once.

It looks like the vibration time doesn't matter (tried 3, 10, 100, 500, and 5000).

If i set the vibration time to a particularly high value (eg.5000), the error message appears before the vibration ends.