Could you provide your environment information that you can see on /admin/info page? It is even better if you provide errors in production.log.
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Confirmed the problem. You can create an issue but you will see Internal Server Error when accessing issues#show page.

<pre>
Processing by IssuesController#show as HTML
Parameters: {"id"=>"20368"}
Current user: admin (id=1)
Rendered issues/_action_menu.html.erb (4.8ms)
Rendered issues/show.html.erb within layouts/base (2326.0ms)
Completed 500 Internal Server Error in 2394ms (ActiveRecord: 52.4ms)

ActionView::Template::Error (too big number for repeat range: /^ {100001}\S/):
85:
86: <p><strong><%=l(:field_description)%></strong></p>
87: <div class="wiki">
88: <%= textilizable @issue, :description, :attachments => @issue.attachments %>
89: </div>
90: </div>
91: <% end %>
lib/redmine/wiki_formatting/textile/redcloth3.rb:1037:in `flush_left'
lib/redmine/wiki_formatting/textile/redcloth3.rb:1031:in `clean_white_space'
lib/redmine/wiki_formatting/textile/redcloth3.rb:293:in `to_html'
lib/redmine/wiki_formatting/textile/formatter.rb:43:in `to_html'
lib/redmine/wiki_formatting.rb:89:in `to_html'
app/helpers/application_helper.rb:656:in `textilizable'
app/views/issues/show.html.erb:88:in `_app_views_issues_show_html_erb__2452628678795344758_70339042017100'
app/controllers/issues_controller.rb:106:in `block (2 levels) in show'
app/controllers/issues_controller.rb:99:in `show'
lib/redmine/sudo_mode.rb:63:in `sudo_mode'
</pre>
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The issue is reproducible when the text formatting setting is Textile. No problem if the setting is Markdown.
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Here is a workaround.

<pre><code class="diff">
Index: lib/redmine/wiki_formatting/textile/redcloth3.rb
===================================================================
--- lib/redmine/wiki_formatting/textile/redcloth3.rb (revision 17592)
+++ lib/redmine/wiki_formatting/textile/redcloth3.rb (working copy)
@@ -1034,7 +1034,7 @@
def flush_left( text )
indt = 0
if text =~ /^ /
- while text !~ /^ {#{indt}}\S/
+ while text !~ /^ {#{indt}}[^ ]/
indt += 1
end unless text.empty?
if indt.nonzero?
</code></pre>

If the string variable @text@ start with @" \x0b"@, the @while@ loop never ends until some error occurs. It is the cause of the error. The regexp @/^ {1}\S/@ does not match the string @" \x0b"@ because "\x0b" is considered as white-space. In other words, @/\S/@ matches @"\x0b"@ because @"\x0b"@ is a kind of white-space.

Maybe the regular expression @/^ {#{indt}}\S/@ is expected to match preceeding space characters and a character other than space char, so it may be expected to match @" \x0b"@ too. But @\S@ does not match @"\x0b"@. It matches not only space character but @[^ \t\r\n\f\v]@. @"\v"@ is another expression of @"\x0b"@.
--------------------------------------------------------------------------------
Does anyone understand why the implementation of @flush_left@ method is so complicated? I think we can make it simpler like the following:

<pre><code class="diff">
Index: lib/redmine/wiki_formatting/textile/redcloth3.rb
===================================================================
--- lib/redmine/wiki_formatting/textile/redcloth3.rb (revision 17592)
+++ lib/redmine/wiki_formatting/textile/redcloth3.rb (working copy)
@@ -1032,15 +1032,7 @@
end

def flush_left( text )
- indt = 0
- if text =~ /^ /
- while text !~ /^ {#{indt}}\S/
- indt += 1
- end unless text.empty?
- if indt.nonzero?
- text.gsub!( /^ {#{indt}}/, '' )
- end
- end
+ text.sub!(/^ +/, '')
end

def footnote_ref( text )
</code></pre>
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Maeda-san

Thank you for the consideration.
That's exactly the same as my problem. The log looks same as mine.
I will try the suggested workaround. Thank you.

I put my environment info for future reference.

<pre>
Environment:
Redmine version 3.4.4.stable.17236
Ruby version 2.4.3-p205 (2017-12-14) [x86_64-linux]
Rails version 4.2.8
Environment production
Database adapter Mysql2
SCM:
Subversion 1.7.14
Git 1.8.3.1
Filesystem
Redmine plugins:
clipboard_image_paste 1.12
recurring_tasks 2.0.0-pre
redmine_banner 0.1.2
redmine_comment_only 0.0.1
redmine_enter_cancel 0.0.2
redmine_export_with_journals 0.0.8
redmine_issue_templates 0.1.8
redmine_knowledgebase 3.3.1
redmine_pivot_table 0.0.5
redmine_wiki_lists 0.0.9
redmine_wiki_unc 0.0.3
sidebar_hide 0.0.8
view_customize 1.1.4
</pre>

--------------------------------------------------------------------------------
Opps, the cases should be reversed in the description.

* NG case
<pre>
ADDRESS +0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +A +B +C +D +E +F 0123456789ABCDEF
----------+-------------------------------------------------------------------
00000000: 0B 61 62 63 64 65 31 32 33 34 35 20 -- -- -- -- .abcde12345
</pre>

* OK case
<pre>
ADDRESS +0 +1 +2 +3 +4 +5 +6 +7 +8 +9 +A +B +C +D +E +F 0123456789ABCDEF
----------+-------------------------------------------------------------------
00000000: 20 0B 61 62 63 64 65 31 32 33 34 35 20 -- -- -- .abcde12345
</pre>

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
Here is a patch. Added a test to the code in #29756#note-4.
--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
Hide MATSUTANI wrote:
> Opps, the cases should be reversed in the description.

No, cases in the description field are correct. 0x20 and 0x0b at the beginning of a line cause the exception.
--------------------------------------------------------------------------------
Go MAEDA wrote:
> Hide MATSUTANI wrote:
> > Opps, the cases should be reversed in the description.
>
> No, cases in the description field are correct. 0x20 and 0x0b at the beginning of a line cause the exception.

Maeda-san

Sorry, I was confused.
Thank you for preparing patch.

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Committed.
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relates,Closed,32971,New line between list items break a list