Problems with header rows when inserting columns

I frequently have a terrible time with Word tables when I need to 'insert'
columns, especially (but not only) if one or more header rows contains a
merged cell that spans two or more columns.

The kinds of strange results I generally get leave the impression that Word
actually treats header rows as separate tables that are joined to the actual
table's 'data rows,' because the behavior of the header row columns after
attempting such column insertions is often distinct from that of the columns
in the rest of the table.

What I find over and over is that even if the new column inserts more or
less correctly, the header row(s) don't reformat in a way that recognizes it.
In almost all cases, the cell border lines in those header rows end up all
over the place and for some reason are often very difficult to realign with
the non-header row border lines for those columns.

I usually end up 'undoing' the column insertion and instead splitting the
adjacent column and then converting one half of that split column into the
new column. As much work as that can be, it seems to end up better than
trying to use the 'insert column' feature.

Is there any other (better) solution to this?

Thanks.