Database broken after using pgadmin 'backup' on OSX

Hi,

Can anyone help with the following problem?

Since upgrading to pgAdmin 4 v1.5 on macOS Sierra (v10.12.5), it seems my
database is 'broken' every time I use the pgAdmin 'Backup' tool.

Here's what happens:
* macOS Sierra v10.12.5
* postgres 9.6.2 locally installed with brew
* pgAdmin 4 v1.5 installed directly from website
* database is running fine
* use the pgAdmin Tools / Backup... utility to take a full back-up
* database is no longer working

By 'no longer working' it means that the postrges libraries have been
messed up and I get the following error when I try to connect via pyscopg2
(python v3.5.2_3, pyscopg2 v2.6.2):

File
"/Users/conor/virt_env/conor/lib/python3.5/site-packages/psycopg2/extras.py",
line 288, in execute
return super(NamedTupleCursor, self).execute(query, vars)
psycopg2.InternalError: could not load library
"/usr/local/lib/postgresql/plpgsql.so":
dlopen(/usr/local/lib/postgresql/plpgsql.so, 10): Symbol not found:
_DatumIsReadWriteExpandedObject
Referenced from: /usr/local/lib/postgresql/plpgsql.so
Expected in: /usr/local/opt/postgresql/bin/postgres
in /usr/local/lib/postgresql/plpgsql.so

I find the only way to fix the problem is to run "brew switch postgresql
9.6.2". I don't really know what that command does but the database
connections are OK after I run it. Also, the database backup file has been
created successfully as far as I can tell: I have not yet attempted to
restore it. One other thing is I don't get a confirmation message in the
pgAdmin console the way I used to.

Can anybody help with the above problem? It has only started happening
since I upgraded to pgAdmin 4 v1.5. Before that (with pgAdmin 4 v1.4)
everything was fine.

Thanks for your help.

Regards,

Conor McNally