Problem with temporary links to 'Already installed' and internal error

Hi,

We have an ongoing problem that comes and goes. Sometimes a normal link will go to a page that tries to install wordpress and will give an error message ‘wordpress is already installed’. Other times it gives an internal error. Usually these clear if you refresh the page. It has been an issue for a while so is not related to a recent update.

My host has repaired databases when it gets bad, but cannot see why it would be temporary.

Does anyone have any ideas? Have you seen this before? It can be whilst using the main site, though possibly it’s more common in the back end.

Thanks for any help