BUG #15671: The copy command does not load all the lines from a .csv file.

The following bug has been logged on the website:

Bug reference: 15671
Logged by: Эдуард Зенченко
Email address: ezenchenko(at)gmail(dot)com
PostgreSQL version: 10.4
Operating system: Debian 4.9
Description:

Hello!
There is a .csv file in windows-1251 encoding.
The file has 1165988 lines, along with the title.
I need to upload it to the table.
I execute the command in PgAdmin 4:

drop table test_csv;
create table test_csv (addr text, houseid text);
copy test_csv (addr, houseid) FROM '/tmp/gis_fias_kra.csv' (DELIMITER ';',
FORMAT CSV, NULL '\', HEADER, ENCODING 'win1251');

In response, I get:
COPY 993130
Query returned successfully in 7 secs 352 msec.

In table 993130 records.
The file is located in a directory on the server.

Why aren't all the lines from the .csv file loaded? This is very similar to
an error in the application.
The same file was loaded using pgloader, and all lines were loaded.