In an older post, I wrote about how the left margin can disappear when you try to insert a subform in a tabbed table, f.e.
It turns out that this is actually pretty easy to fix if you set the correct margin before inserting the subform.
F.e. the following settings
Once the subform is inserted, altering the margin settings has no effect any more, so if the subform is not positioned as intended, just remove the subform, adjust the margin and reinsert the subform.