Can only aggregate 2 fields using a subquery

I can execute this query:

> SELECT mean(p) AS meanx, count(p) AS countx FROM (SELECT P51+P55 AS p FROM L11)
name: L11
time meanx              countx
---- -----              ------
0    10.283385489169628 17728

I can also execute this query:
SELECT P51+P55+P57 AS p FROM L11

But as seen, this query takes forever:

SHOW QUERIES

qid  query                                                                                   database     duration
---  -----                                                                                   --------     --------
1788 SELECT mean(p) AS meanx, count(p) AS countx FROM (SELECT P51 + P55 + P57 AS p FROM L11) greenbean_dl 5h40m51s
1814 SHOW QUERIES                                                                            greenbean_dl 48┬Ás
>

Is this by intent? Is there another way to do so?

Hello again,

Has anyone experienced anything like this? Should it be happening?

I just upgraded from InfluxDB shell version 1.3.1 to 1.3.5, and the issue remains.

Thanks