We’re in the process of selling our ground-floor leasehold maisonette in a Victorian terrace and have recently had some fairly significant cracks become much more pronounced. We’ve just taken it off the market to try to deal with this issue.   
There has been some historic cracking and a structural engineer inspected the property around 7 years ago, before we bought it, and considered it structurally sound. The cracks have always become a little more noticeable during hot/dry summers, but this year they’ve opened up considerably more than we’ve seen before, & over the last couple of weeks to quite a worrying degree.   
I’ve contacted three structural engineers but haven’t managed to get anyone to come out yet. My dad has suggested going directly through the building’s insurance instead, as the cracks are so concerning…  
I’m worried, though, about the implications of notifying the buildings insurer about possible movement when we’re trying to sell - particularly if it gets recorded as a potential subsidence claim before we even know what the cause is.

\- Has anyone been through something similar?  
\- Would you keep trying to get an independent structural engineer first, or notify the buildings insurer immediately?  
\- Does anyone know how long the investigation/claim process can take?

I’m not looking to hide anything from a buyer - we want to understand what’s happening and get it dealt with properly. I’m just wary of inadvertently making the property much harder to sell by taking the wrong first step. & also want to get it looked at as quickly as possible!

Would appreciate any advice 🫶

Leasehold flat with worsening cracks - structural engineer first or buildings insurance?