Bug/Issue Guild quest stops working - does not record progress

First off, I want to thank Kataris for providing a save of a bugged quest.

Bug: Occasionally, the Guild quest (Initiation, id = 15), will display text suggesting you need to slay 10 slimes, but that won't work.

Diagnostics: To put it simply, if you reach at least level 30 on the first day you go in the mines and have gotten the wizard letter or gotten the joja membership, you have a 1 in 3 chance of triggering this bug.

The bug appears due to the fact that all SlayMonsterQuests auto generate a random quest, which populate details, and then have a few failsafes (especially as the one for Clint appears not to be properly generated....)
which will set up the Wizard and Duggy.

But then it returns back to the quest generating the specific ID, which doesn't properly override the correct field to generate a monster base on that, and then resets the target to null.

It may be triggerable in other ways.

Mitigation:
On the first day you enter the mine, don't go beyond level 10.