I think I have found a bug in the current version of Word 365. If you have a linked excel and preserve formatting selected, the formatting breaks when inserting a line in the table.
Steps to reproduce:
Step1:
Create blank excel document
Create a simple table of data in Excel
Select the table and give it a bookmark name:

Save the file
Step2:
Link this into word and update the source of the link to use the reference instead of a row set.
Set the table layout to "Autofit Window"

Step 3:
In excel, insert a new row in the table. Return to word and the table formatting is broken on the last line of the table. It is always the last line which has broken formatting irrespective of where the new line is inserted

Note: there is a number of secondary bugs here as well.
1 - When changing the source link on a linked excel in word, if you enter a filename first, after selecting "item", the file name loses its extension.
2 - If you don't use a bookmark but simply reference "Table1" it adds 3 columns and 3 rows to the table which is copied over to word.
3 - If you choose to keep the source formatting and then set the table in word to fit to window, the table loses its fit to window formatting on update, but there is no way in excel to specify fit to window.
Anyway if someone could verify this?
Thanks