After a pawn is removed from the "Daycare" class type, and the class is deleted the pawn's timetable doesn't get properly reset, leaving it with less than 24 entries. This causes an error when trying to open the "Schedule" maintab in the game, making it impossible to fix in-game. The only way I've found is to manually edit the save file to fix the timetable to have 24 entries again.
An example error log when trying to open the corrupted timetable:
https://pastebin.com/vqWvmUKn

This also causes issues during the times when the pawn is missing it's timetable entries. It doesn't break the game, but during the period where the pawn doesn't have a schedule the game keeps throwing errors if in dev mode and the pawn just wanders around aimlessly.

Example of corrupted timetable from the save:
<timetable>
<times>
<li>Anything</li>
<li>Sleep</li>
<li>Sleep</li>
<li>Sleep</li>
<li>Sleep</li>
<li>Sleep</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
<li>Anything</li>
</times>
</timetable>


For anyone looking for a temporary fix until the authors can sort this out:
Open your save file, search for the pawn's last name like this: <birthLastName>Luzaj</birthLastName>
Then you have to keep scrolling down until you find the <timetable> entry. If you're not sure which of your pawn has a corrupted timetable then you have to check them all and count if they have 24 entries in it. For any pawn that that has less than 24 entries, just add new <li>Anything</li> lines until they have 24 entries. Save the file and it should be fixed.