Problems with multiple larger files

I have pro version and all working fine until I try to upload multiple larger files – say 24 files of around 2.5mb each
After the first few files have uploaded the progress bar stops working and only the first few files are listed in the drop down list.
When I check on the server I can see that the files are still uploading and most of the time it completes (though not always) However the user isn’t provided with any feedback.
On Firefox it eventually crashes the browser and Interet explorer just becomes non-responsive
Here is my shortcode

[wordpress_file_upload uploadpath="../subs_photos/%username%/%userdata1%" uploadrole="administrator,subscriber,editor" uploaduser="all" uploadpatterns="*.jpeg,*.jpg" createpath="true" forcefilename="true" dublicatespolicy="maintain both" adminmessages="true" debugmode="true" placements="title/userdata/filename/selectbutton/uploadbutton/progressbar/message" widths="filename:200px, progressbar:200px,userdata:200px" heights="filename:200px" userdata="true" userdatalabel="Job Ref:|t:text|s:top|r:1|a:0|p:right|d:"]

I thought maybe if I added the gallery underneath, the page reload might sort out the problem. But gallery isn’t showing at all?
Shortcode I tried for this is:
[wordpress_file_upload uploadpath="../subs_photos/%username%/%userdata1%" uploadrole="administrator,subscriber,editor" uploaduser="all" uploadpatterns="*.jpeg,*.jpg" createpath="true" forcefilename="true" dublicatespolicy="maintain both" gallery="true" postlink="true" forceclassic="true" adminmessages="true" debugmode="true" placements="title/userdata/filename/selectbutton/uploadbutton/progressbar/message" widths="filename:200px, progressbar:200px,userdata:200px" heights="filename:200px" userdata="true" userdatalabel="Job Ref:|t:text|s:top|r:1|a:0|p:right|d:"]

Server settings are:
max_execution_time 60
max_input_time 60
post_max_size 50M
memory_limit 128M
upload_max_filesize 50M

I’ve also added the following to the theme’s function.php file

@ini_set( ‘max_execution_time’, ‘300’ );
@ini_set( ‘max_input_time’, ‘300’ );

Upload Big Files in Chunks is On

https://ww.wp.xz.cn/plugins/wp-file-upload/