BUG #14461: ERROR: index returned tuples in wrong order

The following bug has been logged on the website:

Bug reference: 14461
Logged by: Nicholas Wilson
Email address: nwilson5(at)gmail(dot)com
PostgreSQL version: 9.6.1
Operating system: Ubuntu 16.04
Description:

Just to clarify, I'm having this issue on Postgresql 9.6.1 and 9.5.5. But
the error does not occur on 9.4.6 and 9.4.10 for me. Happens on both Ubuntu
14.04 and 16.04 for me.

On 9.5 or 9.6, Postgis versions 2.3.1 on 9.6 and 2.2.2 on 9.5. On 9.4 I was
using Postgis 2.3 also on Postgresql 9.4 and it worked fine... I can easily
replicate the error as follows:

test=# create extension postgis;
test=# create table test (geo geometry);
test=# insert into test values
('0101000020E61000007D91D0967329E4BF6631B1F9B8D64A40'::geometry),
('0101000020E6100000E2AFC91AF510C1BFCDCCCCCCCCAC4A40'::geometry);
test=# create index on test using gist (geo);
test=# vacuum analyze test;
test=# set enable_seqscan = false;
test=# select * from test ORDER BY geo::geometry <->
('0101000020E610000092054CE0D6DDE5BFCDCCCCCCCCAC4A40'::geometry);
ERROR: index returned tuples in wrong order

The different builds I used/tested are listed below with their corresponding
Postgis versions. I asked in IRC with no response if this were something I
should report to Postgresql or not (thought maybe due to the fact that it
only errors on certain Postgresql versions even when given the same postgis
version).

SELECT PostGIS_full_version();

Postgresql 9.6.1 (ERRORS):
POSTGIS="2.3.1 r15264" GEOS="3.5.0-CAPI-1.9.0 r4084" PROJ="Rel. 4.9.2, 08
September 2015" GDAL="GDAL 1.11.3, released 2015/09/16" LIBXML="2.9.3"
LIBJSON="0.11.99" (core procs from "2.3.0 r15146" need upgrade) TOPOLOGY
(topology procs from "2.3.0 r15146" need upgrade) RASTER (raster procs from
"2.3.0 r15146" need upgrade)

Postgresql 9.6.1 (ERRORS):
POSTGIS="2.3.1 r15264" GEOS="3.4.2-CAPI-1.8.2 r3921" PROJ="Rel. 4.8.0, 6
March 2012" GDAL="GDAL 1.10.1, released 2013/08/26" LIBXML="2.9.1"
LIBJSON="0.11.99" RASTER

Postgresql 9.5.5 (ERRORS):
POSTGIS="2.2.2 r14797" GEOS="3.5.0-CAPI-1.9.0 r4084" PROJ="Rel. 4.9.2, 08
September 2015" GDAL="GDAL 1.11.3, released 2015/09/16" LIBXML="2.9.3"
LIBJSON="0.11.99" RASTER

Postgresql 9.4.6 (OK):
POSTGIS="2.1.8 r13780" GEOS="3.4.2-CAPI-1.8.2 r3921" PROJ="Rel. 4.8.0, 6
March 2012" GDAL="GDAL 1.10.1, released 2013/08/26" LIBXML="2.9.1"
LIBJSON="UNKNOWN" (core procs from "2.1.7 r13414" need upgrade) TOPOLOGY
(topology procs from "2.1.7 r13414" need upgrade) RASTER (raster procs from
"2.1.7 r13414" need upgrade)

Postgresql 9.4.10 (OK):
POSTGIS="2.3.1 r15264" GEOS="3.5.0-CAPI-1.9.0 r4084" PROJ="Rel. 4.9.2, 08
September 2015" GDAL="GDAL 1.11.3, released 2015/09/16" LIBXML="2.9.3"
LIBJSON="0.11.99" RASTER

Excuse me if this were more appropriately reported to Postgis. I saw a
related old report with them regarding this issue, but it was specified as
only being an issue on Postgresql 9.5.