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" repeatedly fails 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 explicit type 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

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Best regards

Thomas Butz