Can you run all of the records if you only run it with limited number of rows or does it always fail when it gets to the 90K point? Is this problem only for one set of data that you are trying to insert where you have to limit it?

Error seems to be that in your code you are converting / casting a value to nvarchar datatype which the size of your nvarchar field seems to small for. Check the data that you are pulling and test the length and check that your field in your UDTT is large enough to hold your values.