Not sure what could be an issue then, need to investigate that directly on your site. That is not a common issue, which could be replicated. You could use paid support in Settings/Support tab.
Another suggestion which could help is to reimport properties to your site. Probably something wrong whith one particular property(again I mean probably it was corrupted in your database) which is causing that error.
So when you will start new import you could delete all properties from the site first(there is an option for that).
After that disable that option, so in future, you won’t be deleting all properties on each import
Regards.
