EventLogging is reporting failures, and the problem seems to be the following (already decoded):
Unable to validate: ?{"event":{"pagename":"Recentchanges","hidepatrolled":true,"namespace":"0"},"schema":"ChangesListFilters","revision":[REDACTED],"clientValidated":false,"wiki":"hewiki","webHost":"he.wikipedia.org","userAgent":"REDACTED"}; cp1066.eqiad.wmnet 6020266 2017-01-01T11:16:03 - "MediaWiki/1.29.0-wmf.6" (u'0' is not of type 'integer')
(the REDACTED parts can be found in the logs on eventlog1001).