Form is not working


We have a lot of forms that get used daily, but we are having random problems with this one sheet/form, a couple different things will happen and it is at random:

1) if two forms are uploaded close to one another, only the first one will come in and the second one will not submit and it gets lost.

2) They will upload one and it will get uploaded twice.

3) Sometimes they will not upload at all even though they will get confirmation that it was successfully  submitted.

All of them get submitted to the top of the sheet, there is no hiden rows/columns, and no filters are on. What can be fixed?