HS Bioanalyzer peak drops into negative

[SeqTroubles]

Hi All,

I am after performing a nextera xt library prep and I am running a HS chip at the moment. The samples produce weak scratchy peaks but when they come back down it goes into the negative space.

Now the kit I am using is expired but I made fresh gel today and the ladder had worked perfect. Is it worth re-testing with a fresh kit?

Thanks