Girls' Frontline production anomaly.

Today I was looking at the GFDB and noticed something strange: there were some results that just weren't supposed to happen:
1 (one) [SMG] C-MS each from HG recipe 130-130-130-130 and AR recipe 97-404-404-97,
1 (one) [SMG] 100 Shiki each from HG recipe 130-130-130-130 and AR recipe 91-400-400-30,
1 (one) [AR] MDR from SMG recipe 400-400-91-30.

I could think of several reasons for that:

• Magic
• MICA's shady new crafting formula
• Tester-kun is fooling around again
• It's an Arknights conspiracy

As you probably know, templates like that are forbidden. At first I was afraid that my SQL import process failed because I tried to speed it up so much that what was left of a full json parser was a basic tokenizer which didn't even check field names, assuming that their order was deterministic and could only change because of some server maintenance or update. Fortunately I keep complete raw logs. One search later I confirmed that no, import was doing fine, and the anomaly shows up there too. If you're curious, here are the crafts in question:

{"id":"11027121","dev_type":"0","user_id":"52674","build_slot":"1","dev_uname":"Lani","dev_lv":"63","gun_id":"228","mp":"91","ammo":"400","mre":"400","part":"30","input_level":"0","item1_num":"1","core":"0","dev_time":"1555766798"} {"id":"11002254","dev_type":"0","user_id":"91144","build_slot":"1","dev_uname":"AdultNeptune","dev_lv":"126","gun_id":"215","mp":"400","ammo":"400","mre":"91","part":"30","input_level":"0","item1_num":"1","core":"0","dev_time":"1555755557"} {"id":"10986940","dev_type":"0","user_id":"599614","build_slot":"1","dev_uname":"uwux3usowarm","dev_lv":"33","gun_id":"213","mp":"130","ammo":"130","mre":"130","part":"130","input_level":"0","item1_num":"1","core":"0","dev_time":"1555750872"} {"id":"10554813","dev_type":"0","user_id":"5795","build_slot":"1","dev_uname":"Arveene","dev_lv":"117","gun_id":"213","mp":"97","ammo":"404","mre":"404","part":"97","input_level":"0","item1_num":"1","core":"0","dev_time":"1555806667"} {"id":"10468473","dev_type":"0","user_id":"317635","build_slot":"1","dev_uname":"Eoneo","dev_lv":"158","gun_id":"228","mp":"130","ammo":"130","mre":"130","part":"130","input_level":"0","item1_num":"1","core":"0","dev_time":"1555751142"}

There is nothing particularly suspicious in the data: all userids are different (they do belong to 2 out of 10 shards, but that's not quite enough), times are quite far apart (doesn't look like particle shower bitflips and AWS hardware should have ECC anyways), no magic numbers indicative of overflow of some kind. I don't know what caused this yet.