Again - there could be many reasons for these oddities - character meals may not be quite as popular during September/October along with restaurants in EPCOT due to the Food and Wine festival. More adults will travel during this time. But as before, the main driver is
free dining, plus a whole bunch of complicated secondary factors. If you can give some examples of which restaurants you find particularly bizarre, then I'm sure some other regulars can confirm their experiences. But availability dropping off and coming back on is very likely in free dining. For example, I have around 50 ADR's for this October (as in 50 different restaurant bookings). I have had the IPO changing things around all the time as the inventory changes, which causes a ripple effect. For example, a BoG reservation opened up for 08:05, so the IPO cancelled my Kona Cafe registration and booked the BoG reservation. Someone else probably then shifted their dining reservations around to snag my Kona Cafe registration, etc etc. So just 1 person changing their dining reservation can probably cause a ripple of about 20 other changes. If you think that just me (1 of many tens of thousands of guests on the dining plan) has 50 ADR's, this goes a long way to explain why there's no availability.