All city walls.

I cant imagine 1.3 would be causing the problem, all I can say is double-check your descr_campaign_db.xml

I've double checked all the files in my experiments mod and have found nothing elts that it could be. Here's the seltments and crusades parts of my descr_campaign_db.xml, maybe there's something in there I'm missing.
<settlement>
<sack_money_modifier float="0.4"/>
<exterminate_money_modifier float="0.5"/>
<chiv_spf_modifier float="1.0"/>
<chiv_sof_modifier float="1.0"/>
<dread_sof_modifier float="-1.0"/>
<piety_cor_sif_modifier float="1.0"/>
<piety_admin_sif_modifier float="1.0"/>
<port_to_port_mp_min float="100.0"/>
<heresy_unrest_modifier float="35.0"/>
<religion_unrest_modifier float="15.0"/>
<siege_gear_required_for_city_level string="huge_city"/>
<siege_gear_required_for_castle_level string="moot_and_bailey"/>
<no_towers_only_for_city_level string="huge_city"/>
<no_towers_only_for_castle_level string="moot_and_bailey"/>
<min_turn_keep_rebel_garrison int="25"/>
</settlement>
<crusades>
<required_jihad_piety int="4"/>
<max_disband_progress float="10.0"/>
<near_target_no_disband_distance float="10.0"/>
<disband_progress_window float="3"/>
<crusade_called_start_turn float="20"/>
<jihad_called_start_turn float="20"/>
<movement_points_modifier float="2.0"/>
</crusades>
I am using unmoded;
descr_mercenaries.txt
descr_recruitment.xml
descr_settlement_mechanics.xml
and
export_descr_unit.txt

I cant think of any other files that may influence this.