From the event logging I see ~150 instances of 'internal_api_error_DBQueryError'
To debug, some samples are given below
en->ta
tawiki
timestamp: 20160410071417
Source title: Laminar armour
{"servedby":"mw1115","error":{"code":"internal_api_error_DBQueryError","info":"[1d159c53da9eb0eeb620cb98] Database query error"},"errorCode":"internal_api_error_DBQueryError"}
en->ml
mlwiki
timestamp: 20160502174123
Source: Teacup
{"servedby":"mw1143","error":{"code":"internal_api_error_DBQueryError","info":"[VyeRQgpAEHsAAD5Z@8gAAAAV] Database query error"},"errorCode":"internal_api_error_DBQueryError"}