Relevant xkcd
Pasting a selection from Excel into Smartsheet fails to find the end of row if you include (1) double quotation mark ( " ). See below.

As an example, pasting the data above from Excel to a Smartsheet grid produces the following result:

It appears that Smartsheet is not catching and escaping these characters, causing all data beyond the quote mark to become one very long row. Two double quotes ( " " ) does not generate this error, nor does use of a single single quote / apostrophe ( ' ).