Updating to 8.6.1 – something happened this time

I took the steps to migrate an 8.5.6 site to the newest 8.6.1 version.

I did what I’ve done in the past, that is:

1) manually replace (via FTP) the directories ‘core’ and ‘vendor’ with the new versions and then

2) run www.lexhamarts.org/update.php.

This has always worked in the past. 

This time, however, when I tried to run update.php, I get a 

www.lexhamarts.org is currently unable to handle this request.



The server error log lists:
PHP Parse error: syntax error, unexpected end of file in /home/xyz/public_html/vendor/composer/autoload_static.php on line 435

Any ideas or can you point me in the right direction?


Drupal version: 

Source: https://www.drupal.org/taxonomy/term/21/feed