Autovacuum analyze can't find C based function

While installing Nominatim(OSM geocoding service) I stumbled upon this issue:
https://github.com/openstreetmap/Nominatim/issues/1097#issue-341799919

The function "transliteration" has been properly created during the installation processes according to the following
template:
https://github.com/openstreetmap/Nominatim/blob/v3.1.0/sql/functions.sql#L25

The strange thing is that i'm able to execute the function while background analyzation of the table "placex"
repeatedlyfails with the following error: 

2018-07-17 06:59:35.908 UTC [30641] ERROR:  function transliteration(text) does not exist at character 23
2018-07-17 06:59:35.908 UTC [30641] HINT:  No function matches the given name and argument types. You might need to add
explicittype casts. 
2018-07-17 06:59:35.908 UTC [30641] QUERY:  SELECT gettokenstring(transliteration(name))
2018-07-17 06:59:35.908 UTC [30641] CONTEXT:  PL/pgSQL function public.make_standard_name(text) line 5 at assignment
        automatic analyze of table "nominatim.public.placex"

I can execute the same function without an error in a psql session though:

# psql -d nominatim -U www-data -c "SELECT transliteration('some w€êîrd text')"
 transliteration
-----------------
 some weird text
(1 row)

Restarting the database stops the anaylze errors from occurring.

Postgres:  10.4
Postgis:    2.4
Nominatim: 3.1.0

--
Best regards


Thomas Butz