Who here has worked with Gel Electrophoresis? I need some help with an issue on one of my gels, and I need to know the cause and impact outside of what is immediately obvious.

Redacted main bands for data integrity. These are two lanes of my gel - left one is a blank, to provide comparability for gel background. The right one is my sample. The two bands are the dyefront (thinner band) and a mystery band (thicker, wide band below the dyefront). This artifact is not present in other lanes on the gel with similar samples, and my colleagues who've been in the field a long time have no clue what it is. Has anyone chanced upon an issue like this one? The gel ran fine, reagents are all prepped correctly and are within expiry. Have you ever seen something run ahead of the dyefront in this manner? The band's components MWs would have to be less than 2.5 kDa, which floors me. Is it just a fluke of random shit, somehow in the sample well before running?