Missing submissions on KoboToolbox

I've built a form using xlsforms, upload it to kobo.humanitarianresponse.info and gave access to 12 users to do submissions from their phones.
After a while, I realized that one user has sent a lot of submissions and I only received few. (less than 10% of what he submitted). I tried to figure out what is the problem and asked him to submit new forms and check if I will receive them or not, and everything was working well. after a couple of weeks, I found that the missing submissions have arrived and appeared in form data with the lowest index( starting from 1) and the other index has shifted. Meanwhile, I'm facing the same problem with another user.

Please advice me on how can I get those missing forms and your efforts are appreciated.

Hi @Mohamad_Eido

you can try to resent forms from Send Finalized Form -> Change View -> Show Sent and Unsent Forms

but generally, if you use kobo-toolbox please ask there http://help.kobotoolbox.org/

Unfortunately, I've asked KOBO support but there is no response till now.