Sometimes it auto ticks buy resources if not enough..so that explains the missing coupons. Also if u have shared your account details..some jealous person could spend your coupons.If it is none of the above, then contact support using ? and they can look at your spending log and compensate if it is infact a bug. Good luck .

Nope I did not spend them last time, had no shared account, and never had the auto buy resources screwed with me so hard so It is indeed a bug because I heard from my Friend Kessho about her friend that saved up from 2016 and to a low point of 106 coupons, so it is indeed a bug.

Hello, did you happen to use the auto-upgrade option on anything? This sometimes like to automatically turn on, so you need to ensure that it is turned off every time you go to use it.

No I did not turn on the auto upgrade on anything and this has happened twice already with no correlation what so ever, technically both occurrences were near 2000 coupons the day before and the next day over I'm at very low triple digits. Its ridiculous and I very much remembering from not spending on anything regard threads, charms, Cave Keys, or anything of the like ... it just happens like that.