Thanks Dejan. When I asked this question, data security plans did not exist. It seems that "background backup" was accidentally added and set by default in 8.1, but it has reverted back to normal behaviour in versions since then.
More explanation @Paul:
When the issue occurs, should see if restarting presence or lookup helps. If so - that is the issue and should be sorted. First need to ensure that that is the issue...
Hello!
You can mark it as closed as option. If document is connected with other documents you can not delete it so you will not be able to delete PO, as you will not be able to remove Goods receipt...