FileMaker does not permit two users to edit the same record at the same time. This is typical for any database application that supports access by multiple simultaneous users. When a user enters a field and starts editing it, that record is "opened" for editing. Until they commit records, open a different record for editing, change layouts, etc, editing by other users will not be allowed and they will not be allowed to put the focus in a field of that record. For IWP users, this should happen automatically when they click a button to submit the data back to FileMaker.
This can also happen if you have two windows open to the same record for the same user. If you open a record in window 1 and then switch to window 2 and try to modify the data in the same record, you'll get this same message.
This can get complicated when there is a portal involved as I believe that it is still the case that opening the parent record can also lock the portal records, but I haven't check this in a long time so I may not be correct about that. Editing a global field can also sow confusion since each user get's their own "independent virtual copy" of the data in a global field, but editing a global field still opens a record of that table for editing and this can then trigger the edit lock in certain circumstances.
When someone selects a record by clicking on a field, Filemaker locks that record so no one else can make changes until all fields in the record are committed. This becomes very annoying when that person goes on a lunch.
The different Users are on different records with different log-ins. The layout does not use a portal. But they are using IWP.
They enter some data, Click a button which runs a script that goes to a new tab. This has worked for 66 tabs today.
"different log-ins" makes no difference. All it takes is for a user to try to modify a record that another user--which can be another IWP user, a FileMaker Pro client or a FileMaker Go client has already opened for editing. And keep in mind that a single layout can show data from more than one table so it may not be obvious that the two users are trying to modify the same record.
Another source of Edit Locks can be "batch update" operations. Replace Field Contents, for example will briefly edit lock each record that it updates and will, in turn, be locked out of changing an individual record if another user or window has that record open for editing at the instant it tries to modify the record