Hi,
after upgrading from CentOS 7.3 to 7.4 i can see some strange behavior with the macro placeholder images.
The content is not wrong or has some issues but when i go to the edit mode then i get encoding error while rendering the macro placeholder images.
Like this (codeblock macro)

But i can use the macro and edit it without a problem. Also the content is saved to the database and can be viewed without a problem.
The only thing which happend during the last 4 weeks was an upgrade from CentOS 7.3 to 7.4.
I checked with a new CentOS 7.4 VM and a clean install of confluence but got the same misbehaviour.
Setup:
CentOS 7.4
Confluence 6.3.4
PostgreSQL 9.5
Nginx
>> locale
LANG=en_US.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=
setenv.sh
CATALINA_OPTS="${CATALINA_OPTS} -Dfile.encoding=UTF-8"
admin/encodingtest.action
shows no error ==> everything is fine
Test-Setup with the same behaviour:
CentOS 7.4
Confluence 6.3.4 and Confluence 6.4.1
embedded H2 database
Nginx
Also tried to get the image without nginx and got the same result.