TS16 spontaneously rebooting.

Here’s an odd one:

We have 12 portserver TS16’s. We have one slot that the unit spontaneously reboots for no reason we can tell. And it is, of course, our most critical one.

We put the latest firmware in our spare TS16, loaded the configuration and replaced the TS16 in question Tuesday (2 days ago). Sure enough, the new TS16 has spontaneously rebooted twice since then.

Any thoughts as to what may be causing this behaviour? My first thoughts were watchdog timers or other conditionals, but I can find nothing in the documentation to support this. Are there any watchdog timers or other conditionals in the TS16s?

How would we begin diagnosing this?