Can someone please confirm / deny if there is a cell limit (or any other kind of size restriction) when importing flat files into SQL Server?

I have been having an exasperating time recently, importing csv files which continually return the error "Could not convert to nvarchar, data would be truncated"... obviously that error message doesn't help, so I put error reporting on, and noticed that it routinely errored between rows 300 and 330... regardless of file.

I must've put 20 files in and got the same error, always at the same roughly the same row range. I have manually checked every file - there is no obvious cause for that error message in that cell range in any of the files.

My files aren't large (<1mb), contain mainly nvarchar data, and are limited to 500 rows... they are however quite wide (250 cols), leading me to wonder if there's a cell limit?

I tried chopping the files in two, so they were ~250 rows each, and - like magic - they import without issue.

Before I change the process that produces these files, can someone confirm if my suspicion is correct? (Or suggest an alternative cause?)

Edit - Using the built in "Import Flat File" Wizard in SQL Server 15.0. Comma separated; double-quotes; not sure re single quote in the string because the text is in Spanish and they don't use apostrophes!

Edit 2 - probably best to close this one now. A lot of logical suggestions which mirror the troubleshooting I've been doing. That is at least reassuring that it's not an obvious oversight.