I have a multipage form and all works fine. I added a file uploader in a intermediate page and does not works the upload.
In the last page the uploader work fine but not in a intermediate page.
J 2.5.16 - 4.0 RC3.5.2
look the debug, the field is "input_file_108"
Array
(
[lang] => it
[chronoform] => DOPAU2-backup
[event] => submit
[cf_sid] => 6f21f9cfcfb9b3b60459402e6fee7d47
[Itemid] => 375
[option] => com_chronoforms
[view] => form
[input_radio_91] => D
[input_radio_93] => A
[input_checkbox_group_95] => A
[input_radio_97] => Si
[input_radio_99] => C
[input_radio_101] => A
[input_radio_103] => Si
[input_radio_104] => No
[input_submit_20] => Submit
[aae5d57dafb69804d9c0da7e4054ef64] => 1
[language] => it-IT
[_PLUGINS_] =>
[task] => submit
[cb] => 28
[cf_id] => 28
[cf_uid] => 849acbe35887cbc6cca8e10ac6ecd041
[cf_created] => 2013-11-14 15:42:35
[cf_modified] => 0000-00-00 00:00:00
[cf_created_by] => 62
[cf_modified_by] => 0
[cf_ipaddress] => 2001:760:0:158:3e07:54ff:fe4b:42c3
[cf_user_id] => 62
[input_submit_6] => Avanti
[input_text_9] => pincopallo oooo
[input_text_10] => B
[input_text_11] => N
[input_submit_7] => Avanti
[input_text_5] => 34534
[input_select_13] => 1
[input_submit_15] => Avanti
[back] =>
[input_textarea_18] => sfds
[input_radio_19] => A
[input_checkbox_group_28] => A
[input_radio_30] => No
[input_checkbox_group_32] => choice 2,choice 3
[input_checkbox_group_34] => A,B
[input_radio_36] => No
[input_radio_38] => A
[input_radio_40] => A
[file_upload] =>
[input_textarea_44] => sdfsf
[input_submit_47] => Avanti
[input_checkbox_group_50] => A
[input_radio_60] => SI
[input_checkbox_group_54] => A,B
[input_radio_61] => D
[input_radio_62] => E
[input_radio_63] => C
[input_radio_65] => E
[input_radio_67] => SI
[input_radio_70] => C
[input_textarea_72] => sdfsdf
[input_submit_74] => Avanti
[input_checkbox_group_77] => B
[input_checkbox_group_79] => E
[input_checkbox_group_81] => A
[input_checkbox_group_83] => E
[input_checkbox_group_85] => A
[input_textarea_87] => sdfsdf
[input_submit_88] => Avanti
[cc_form_extension] => edit
[input_file_108] =>
[chronoform_data] => Array
(
[cf_modified] => 0000-00-00 00:00:00
[cf_modified_by] => 0
[lang] => it
[chronoform] => DOPAU2-backup
[event] => submit
[cf_sid] => 6f21f9cfcfb9b3b60459402e6fee7d47
[Itemid] => 375
[option] => com_chronoforms
[view] => form
[input_radio_91] => D
[input_radio_93] => A
[input_checkbox_group_95] => A
[input_radio_97] => Si
[input_radio_99] => C
[input_radio_101] => A
[input_radio_103] => Si
[input_radio_104] => No
[input_submit_20] => Submit
[aae5d57dafb69804d9c0da7e4054ef64] => 1
[language] => it-IT
[_PLUGINS_] =>
[task] => submit
[cb] => 28
[cf_id] => 28
[cf_uid] => 849acbe35887cbc6cca8e10ac6ecd041
[cf_created] => 2013-11-14 15:42:35
[cf_created_by] => 62
[cf_ipaddress] => 2001:760:0:158:3e07:54ff:fe4b:42c3
[cf_user_id] => 62
[input_submit_6] => Avanti
[input_text_9] => pincopallo oooo
[input_text_10] => B
[input_text_11] => N
[input_submit_7] => Avanti
[input_text_5] => 34534
[input_select_13] => 1
[input_submit_15] => Avanti
[back] =>
[input_textarea_18] => sfds
[input_radio_19] => A
[input_checkbox_group_28] => A
[input_radio_30] => No
[input_checkbox_group_32] => choice 2,choice 3
[input_checkbox_group_34] => A,B
[input_radio_36] => No
[input_radio_38] => A
[input_radio_40] => A
[file_upload] =>
[input_textarea_44] => sdfsf
[input_submit_47] => Avanti
[input_checkbox_group_50] => A
[input_radio_60] => SI
[input_checkbox_group_54] => A,B
[input_radio_61] => D
[input_radio_62] => E
[input_radio_63] => C
[input_radio_65] => E
[input_radio_67] => SI
[input_radio_70] => C
[input_textarea_72] => sdfsdf
[input_submit_74] => Avanti
[input_checkbox_group_77] => B
[input_checkbox_group_79] => E
[input_checkbox_group_81] => A
[input_checkbox_group_83] => E
[input_checkbox_group_85] => A
[input_textarea_87] => sdfsdf
[input_submit_88] => Avanti
[cc_form_extension] => edit
[input_file_108] =>
)
[chronoform_data_cf_id] => 28
)