All Rows hide after insert-row or delete-row

[gmail <g199526 gmail com>]

For one specific sheet of a file.

When Inserting rows or deleting rows the first thing that happens is 
that most lines become hidden; I then need to select all and do an 
"unhide rows"

Insert/delete one row as row1 and all rows become hidden except rows 160 
226 490. There is no obvious difference in the data in those rows.

Insert/delete any row except row1 and all rows become hidden except the 
frozen column header and rows 160 226 490.

About 1100 rows in the sheet, No rows contain formula or conditional 
formatting.

If I copy the data into a new sheet the problem no longer exists!

Does someone have a reason / solution for this behaviour?

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