How long is the connection down? Based on your post I'm guessing it's going down shortly after midnight and not for a span of 25 seconds correct? Is it just the single MR33 or are we looking at multiple across the same network? Since it's a predictable problem presenting within a very small time frame would you be able to long into the dashboard and either do a capture or even ping it to see if the AP goes down or just the clients lose access. It may just be easier to do a factory reset on it and letting it download the configuration again. Make sure you are not on Beta firmware as well, but a factory reset might fix it allowing you to move on.
It's an interesting issue, if it last more than 30 minutes definitely check the scheduling like someone mentioned. It has to be at least 30 minutes before you can schedule it so no short downtime of 5 minutes or so would be possible. I would post more info on it though if you want better responses but cause it's a bit open ended to help troubleshoot.