Thank you again for your help.
So uninstalling the anti-virus software resolved the database issue. As we were using Bitdefender as recommended, what would be your suggestion for an antivirus solution?
I also thought that the network would be the problem with the slow and laggy performance, however the modem is top shelf and relatively new, and all other networking needs are fast and without issue. Unfortunately we can’t run a wired network, however all PC’s are within 5 metres of the modem. Ping tests run fine too.