Full text of commands cut off in /var/log/secure

I’ve got a server that’s using rsyslogd. When looking for commands run by specific users in /var/log/secure, I see that some commands appear to be cut off.

For example, you can see that the beginning of the JSON is cut off here:

Aug 19 16:31:28 server1.example.com journal: root[265681] : documentation","indices":[211,225]},{"text":"parsingJSON","indices":[226,238]},{"text":"GeoTagged","indices":[239,249]}]}},"entities":{"hashtags":[]}},{"created_at":"Thu May 10 17:41:57 +0000 2018","id_str":"994633657141813248","text":"Just another Extended Tweet with more than 140 characters, generated as a documentation example, showing that ["tru? https://t.co/U7Se4NM7Eu","display_text_range":[0,140],"truncated":true,"user":{"id_str":"944480690","screen_name":"FloodSocial"},"extended_tweet":{"full_text":"Just another Extended Tweet with more than 140 characters, generated as a documentation example, showing that ["truncated": true] and the presence of an "extended_tweet" object with complete text and "entities" #documentation #parsingJSON #GeoTagged https://t.co/e9yhQTJSIA","display_text_range":[0,249],"entities":{"hashtags":[{"text":"documentation","indices":[211,225]},{"text":"parsingJSON","indices":[226,238]},{"text":"GeoTagged","indices":[239,249]}]}},"entities":{"hashtags":[]}}] [login: alice]