Slow browser renders after upgrade to v1.2.17

[bwhitfield]

Just completed Mantis upgrade/server migration from Linux Ubuntu to Windows Server 2012 R2. Our Ubuntu was running on old hardware so I migrated over to new Window server which will be a bit easier for me to manage. Everything is working as expected except for a noticeable lag depending on the browser client. The older server config renders almost immediately. In the Windows server config, Firefox is the fastest to render, but IE and Chrome has a significant lag.

For example, clicking "View Issues" will show the filter header immediately but the table lags ~2-5 seconds later. I've enabled the time display and it shows a decent 0.3099 seconds but does not reflect the total browser render time. Any help understanding/resolving the browser lag would be much appreciated.

Version information is as follows:
OS: Server 2012 R2
MantisBT: 1.2.17
MySQL: 5.6.20 (64-bit)
PHP: 5.3.28
Web: IIS 8.5

MantisBT Database Statistics

mantis_bug_file_table = 5504 records
mantis_bug_history_table = 53007 records
mantis_bug_monitor_table = 12 records
mantis_bug_relationship_table = 328 records
mantis_bug_revision_table = 3851 records
mantis_bug_table = 3806 records
mantis_bug_tag_table = 0 records
mantis_bug_text_table = 3806 records
mantis_bugnote_table = 8288 records
mantis_bugnote_text_table = 8288 records
mantis_category_table = 37 records
mantis_news_table = 0 records
mantis_plugin_table = 1 records
mantis_project_file_table = 0 records
mantis_project_table = 4 records
mantis_project_user_list_table = 58 records
mantis_project_version_table = 1158 records
mantis_tag_table = 0 records
mantis_user_table = 41 records
mantis_user_profile_table = 0 records
mantis_user_pref_table = 35 records
mantis_user_print_pref_table = 0 records
mantis_custom_field_project_table = 0 records
mantis_custom_field_table = 0 records
mantis_custom_field_string_table = 1740 records
mantis_filters_table = 187 records
mantis_sponsorship_table = 0 records
mantis_tokens_table = 15 records
mantis_project_hierarchy_table = 0 records
mantis_config_table = 9 records
mantis_email_table = 0 records

[bwhitfield]

Timed old Linux system for comparison when clicking "View Issues" and it is a bit slower (as expected) with less memory usage.

Linux Time w/ MantisBT 1.2.8:
Time: 0.5492 seconds.
memory usage: 7,930 KB

Server 2012 R2 Time w/ MantisBT 1.2.17:
Time: 0.3213 seconds.
memory usage: 10,439 KB

Once again, the noticeable difference is the lag between showing the filter header and display of the table of issues with same browser.