Wrong arrears (utilities) marker on Experian report?

Hey everyone,

I'm applying for a mortgage soon, checked my reports just in case and discovered I have a very odd arrears marker on my Experian report from OVO Energy for 5 months of arrears (assuming that's what 5 means) for around £300. I paid all my bills on time and don't see anything whatsoever in my online account, I definitely never missed a payment with them.

The grid is also weird as the 5 is surrounded with months that are 0, and the amount stated never appears in any bills, emails etc.

Is this going to cause an issue when applying for a mortgage? My other 2 credit reports are clean with no issues.