I managed to log in to the console and catch the culprit in the act, it's a postgres process for the reporting user using 100% CPU.
Known issue? Should I open a support ticket?
> ps aux|grep postgres
postgres 3241 0.0 0.5 48816 5356 ? S Mar20 0:50 /usr/bin/postgres -D /var/storage/pgsql/data
postgres 3247 0.0 3.3 48944 34956 ? Ss Mar20 0:02 postgres: writer process
postgres 3248 0.0 0.1 48816 1092 ? Ss Mar20 0:01 postgres: wal writer process
postgres 3249 0.0 0.1 49112 1352 ? Ss Mar20 0:00 postgres: autovacuum launcher process
postgres 3250 0.0 0.1 6968 1076 ? Ss Mar20 0:40 postgres: stats collector process
postgres 4052 0.0 3.5 49640 37036 ? Ss Mar20 21:02 postgres: reporting reporting [local] idle
postgres 4331 0.0 1.0 50000 10964 ? Ss Mar20 0:00 postgres: postgres smtp 127.0.0.1(38284) idle
postgres 17723 0.0 0.4 50028 4732 ? Ss 17:20 0:01 postgres: postgres smtp 127.0.0.1(53737) idle
postgres 21328 91.6 6.5 88728 67624 ? Rs 17:47 2:10 postgres: reporting reporting [local] SELECT
Edit: This affects 7.402 as well.
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