App script throws Those rows are out of bounds. exception

[no-premium-audi]

Hi All,

We've  an App sheet application which is used to upload files. It uploads files to a google drive location ,and the uploaded files details are updated to a google sheet  which has unique key ,file name as fields, using which we create a folder with unique key and move the files with the unique key into that. The process of moving the files to the folder runs through a time trigger  which runs every 10 minutes ,for which the google sheet is the reference. After moving the files we delete the rows from the google sheet from bottom to top. But when the trigger is running and if some user uploads the files , Then while deleting the rows it is throwing Those rows are out of bounds  exception .I think this is happening when ever there is a mismatch between the no of rows when the trigger started  ,and if the sheet is updated during the trigger run. 

Could any one help on this. 

Thanks