Data messed-up in shared Excel worksheet

We are using Excel small business 2007. We shared a workbook with 12 users. Frequently the data will get jumbled up.

The workbook is used to keep records and update of jobs done.  All information regarding a job will be in a row with different cells for Customer ID, PO No, PO Date, Item Code, Item Type, Sizes, Quantity, Job Progress etc etc. All these fields are in different column.

The Job Progress actually has many column of different process to complete the job. Different users will update different components of a particular job as the job progress.

In one of the columns, there are these Job Number in running sequence. The Job Numbers are alpha-numerical numbers and unique to each job. Any new  jobs will be appended to the bottom of the table with a unique new Job Number. Frequently, the jobs and the job numbers will get jumbled up. For example, a job with Job Number "A1234" will jump to a different row with say a different Job Number "A1100" etc.

We use filter in the table as well. Frequently different users will sort the table according to their preference. Some users may sort by Customer ID, Others may sort by Item Code etc etc. We ruled out the possibility that the messed up of data was due to sorting on part of the table and the other part didn't get sorted.

Any suggestions what has gone wrong?

Many thanks

Fibon