After upgrade - Display Mode: "Full headers"

Hi everyone,
I went through the list but couldn’t find anything on that one.
After upgrading from version 3.2.2 to 3.4.2 alongside updating some
perl libs RT is no longer displaying “Full headers” in the History

Has anybody an idea what went wrong ?

Here’s a dump of the setup:
Perl v5.8.6 under linux
Apache::Session v1.6;
Apache::Session::Generate::MD5 v2.1;
Apache::Session::lock::MySQL v1.00;
Apache::Session::MySQL v1.01;
Apache::Session::Serialize::Storable v1.00;
Apache::Session::Store::DBI v1.02;
Apache::Session::Store::MySQL v1.04;
AutoLoader v5.60;
base v2.06;
Benchmark v1.06;
bytes v1.01;
Cache::Simple::TimedExpiry v0.22;
Carp v1.03;
CGI v3.05;
CGI::Cookie v1.24;
CGI::Fast v1.05;
CGI::Util v1.5;
Class::Container v0.11;
Class::Data::Inheritable v0.02;
Class::ReturnValue v0.52;
constant v1.04;
Cwd v3.01;
Data::Dumper v2.121_02;
DBD::mysql v2.9004;
DBI v1.46;
DBIx::SearchBuilder v1.27;
DBIx::SearchBuilder::Unique v0.01;
Devel::StackTrace v1.11;
Devel::StackTraceFrame v0.6;
Digest::base v1.00;
Digest::MD5 v2.33;
DynaLoader v1.05;
Encode v2.08;
Encode::Alias v2.02;
Encode::Config v2.00;
Encode::Encoding v2.02;
Encode::Guess v2.00;
Encode::Unicode v2.02;
Errno v1.09;
Exception::Class v1.19;
Exception::Class::Base v1.2;
Exporter v5.58;
Exporter::Heavy v5.58;
FCGI v0.67;
Fcntl v1.05;
fields v2.03;
File::Basename v2.73;
File::Glob v1.03;
File::Path v1.06;
File::Spec v3.01;
File::Spec::Unix v1.5;
File::Temp v0.14;
FileHandle v2.01;
HTML::Entities v1.29;
HTML::Mason v1.28;
HTML::Mason::CGIHandler v1.00;
HTML::Mason::Exception v1.1;
HTML::Mason::Exception::Abort v1.1;
HTML::Mason::Exception::Compilation v1.1;
HTML::Mason::Exception::Compilation::IncompatibleCompiler v1.1;
HTML::Mason::Exception::Compiler v1.1;
HTML::Mason::Exception::Decline v1.1;
HTML::Mason::Exception::Params v1.1;
HTML::Mason::Exception::Syntax v1.1;
HTML::Mason::Exception::System v1.1;
HTML::Mason::Exception::TopLevelNotFound v1.1;
HTML::Mason::Exception::VirtualMethod v1.1;
HTML::Mason::Exceptions v1.43;
HTML::Parser v3.43;
HTML::Scrubber v0.08;
I18N::LangTags v0.35;
I18N::LangTags::Detect v1.03;
I18N::LangTags::List v0.35;
integer v1.00;
IO v1.21;
IO::File v1.10;
IO::Handle v1.24;
IO::InnerFile v2.102 ;
IO::Lines v2.103 ;
IO::Scalar v2.105 ;
IO::ScalarArray v2.103 ;
IO::Seekable v1.09;
IO::Select v1.16;
IO::Socket v1.28;
IO::Socket::INET v1.27;
IO::Socket::UNIX v1.21;
IO::Wrap v2.102 ;
IO::WrapTie v2.102 ;
IPC::Open2 v1.01;
IPC::Open3 v1.0106;
lib v0.5565;
List::Util v1.14;
locale v1.00;
Locale::Maketext v1.09;
Locale::Maketext::Fuzzy v0.02;
Locale::Maketext::Lexicon v0.46;
Locale::Maketext::Lexicon::Gettext v0.14;
Log::Dispatch v2.10;
Log::Dispatch::Base v1.09;
Log::Dispatch::Output v1.26;
Log::Dispatch::Screen v1.17;
Log::Dispatch::Syslog v1.18;
Mail::Address v1.65;
Mail::Field v1.65;
Mail::Field::AddrList v1.65;
Mail::Header v1.65;
Mail::Internet v1.65;
Mail::Mailer v1.65;
Mail::Util v1.65;
MIME::Base64 v3.05;
MIME::Body v5.415;
MIME::Decoder v5.415;
MIME::Decoder::NBit v5.415;
MIME::Decoder::QuotedPrint v5.415;
MIME::Entity v5.415;
MIME::Field::ContDisp v5.415;
MIME::Field::ConTraEnc v5.415;
MIME::Field::ContType v5.415;
MIME::Field::ParamVal v5.415;
MIME::Head v5.415;
MIME::Parser v5.415;
MIME::QuotedPrint v3.03;
MIME::Tools v5.415;
MIME::Words v5.415;
Module::Versions::Report v1.02;
Net::Cmd v2.26;
Net::Config v1.10;
Net::SMTP v2.29;
overload v1.02;
Params::Validate v0.76;
POSIX v1.08;
re v0.04;
Regexp::Common v2.118;
Regexp::Common::delimited v2.103;
RT v3.4.2;
RT::Interface::Email v1.02;
Scalar::Util v1.14;
SelectSaver v1.00;
Socket v1.77;
Storable v2.13;
strict v1.03;
Symbol v1.05;
Sys::Hostname v1.11;
Sys::Syslog v0.05;
Text::Autoformat v1.12;
Text::Quoted v1.8;
Text::Reform v1.11;
Text::Tabs v98.112801;
Text::Template v1.44;
Text::Wrapper v1.000;
Time::HiRes v1.65;
Time::JulianDay v2003.1125;
Time::Local v1.1;
Time::ParseDate v2003.1126;
Time::Timezone v2003.0211;
Tree::Simple v1.14;
utf8 v1.04;
vars v1.01;
warnings v1.03;
warnings::register v1.00;
XSLoader v0.02;

Thank you very much

P.S.: Unrelated to the topic, does anyone have an idea how to handle
those guys sending ticket mails with outlook in that damn html
format ? The main problem here is back in outlook the respone ticket
mail is garbage because of the utf8 encoding and fixed html headers
stating iso-8xxx-1