Redmine

Hello, thank you for your time. Is there any maximum allowed text size for any articles?

I just installed latest Docker Redmine to Synology DS918+, and
everytime I try to upload rather long articles (>512 kbytes), Redmine just says "Internal 500 error" and fails to upload.
(I tested uploading 511k, 513k back and forth... and the boundary is almost exactly 512kb. weird..)

I recognized there would be some limitation for text size, (for Bitnami Redmine 3.4.6 for Windows, it's limited but way larger than 512 kbytes)
512 is too short to use...

I would appreciate it if you could give me any comment. Thanks! :)

(below is production.log file content and version)

----------------------------- log file -----------------------------------
Current user: admin (id=1)
Completed 500 Internal Server Error in 146ms (ActiveRecord: 100.1ms)

ActiveRecord::StatementInvalid (Mysql2::Error: MySQL client is not connected: ROLLBACK):
app/models/wiki_page.rb:216:in `save_with_content'
app/controllers/wiki_controller.rb:173:in `update'
lib/redmine/sudo_mode.rb:63:in `sudo_mode'
--------------------------------------------------------------------------

------------------------------ version -----------------------------------
Environment:
Redmine version 3.3.6.stable
Ruby version 2.3.6-p384 (2017-12-14) [x86_64-linux-gnu]
Rails version 4.2.7.1
Environment production
Database adapter Mysql2
SCM:
Subversion 1.8.8
Darcs 2.8.4
Mercurial 2.8.2
Cvs 1.12.13
Bazaar 2.7.0
Git 2.16.1
Filesystem
---------------------------------------------------------------------------