hi,
some checks:
- restart middle tiers,
- after, try to delete order line from table and after from page. the error is the same ?
if yes, start debugger and try to catch error from debugger deleting data directly from table instead of page
it's a phantom read or undeleted data detection i think
look at these statements in debugger mode
IF No.<>'' THEN
Modify(True);
FIND;
MODIFY(TRUE);
COMMIT:
etc. etc.
look at this post about order release function (with same error), might be useful