look at the msgbox changes to show exactly in which work area you are in your exe
the rest should fix your problem with the code mostly aligned to the previous state.
As others have written, other code variants would be faster, tighter and more succinct.

SET SAFETY OFF
*SET EXCLUSIVE on
***USE bookings IN 0 EXCLUSIVE &&I have tried it with and without the exclusive clause. Makes no difference.
***if you have some table previously selected, it is still active and you pack the wong table
local lnSel
lnSel = select()
USE bookings EXCLUSIVE in select("bookings") 
select bookings
DELETE ALL
PACK
IF ISEXCLUSIVE( ) &&Just to check if there is exclusivity. returns .f. each time - no matter what I change around in the code.
 MESSAGEBOX(dbf() + ' Table opened exclusive in ' + alias())
ELSE
  MESSAGEBOX(dbf() + ' Not opened exclusively in ' + alias())
ENDIF
*SET EXCLUSIVE OFF
SET SAFETY ON
*** shared opening or close needed???
USE bookings shared in select("bookings") 
select m.lnSel