ID Numbers in Access and SharePoint question

Hello All,

I have an Access application in which for each new record, I need a sequential id number. Yes, I know this question is out and about out there, BUT, the answers do not seem to fit my app. There are about 5 users, the Access db is local, linked to SP lists. I have an Add Record button on the main form. It adds a new record, then looks up the MAX of ID from the recordsource table, and sets the ID. Like this:

On Error GoTo Command618_Click_Err

  On Error Resume Next
  Docmd.GoToRecord , "", acNewRec
  If (MacroError <> 0) Then
    Beep
    MsgBox MacroError.Description, vbOKOnly, ""
  End If

  Me.MoveID = Me.lumoveid
  Docmd.Save
  Requery
Me.Inventory.[MoveID] = Me.MoveID

Command618_Click_Exit:
  Exit Sub

Command618_Click_Err:
  MsgBox Error$
  Resume Command618_Click_Exit

However, IDs are getting overwritten or mixed up while others are entering data. The delay between the cloud and the local machine I think is the biggest problem, but I'm wondering what else I could be missing? I have developed Access databases for 27 years - this is my first using SharePoint as a backend. I can only read so much so fast (3 aneurysms contribute to that), so if someone could direct me to a simple solution, that would be so awesome!