There are some weird errors in the logs:
Error status code: -1, Error in REMOVE on a database file ‘c:\Program Files\Couchbase\Server\var\lib\couchbase\data@2i\ticketing2
_seatIdIndex_4910397343005207096_0.index\data.fdb.2’, errno = 32: 'The process cannot access the file because it is being used by another process.
Did this system run out of disk space before/at the time you observed the issue?
Regarding the other error:
2018-04-18T09:48:05.368+03:00 [Error] Flusher::processUpsert Error indexing Key: id1 id2 etc
This happens if your secondary key in array index is too large. You can read this post for more information: