Thanks xpert trailer and Gunner! What you say about the program doesn't sound very promising, but hopefully that doesn't become more of an issue for us... would be great if nch responded with an update to fix the bug!?
We eventually managed to solve our issue! So for anyone else with the same problem... I noticed that MsMpEng.exe was hogging CPU usage when I hit the update button, for Express Accounts to to update with Inventoria, until the program gave "not responding" and "Synchronization Error - Server failed to respond to connection attempt". MsMpEng.exe is associated with Windows Defender, therefore, to solve the problem I added both expressaccounts.exe and inventoria.exe as exclusions under windows defender settings. So far, so good!
Cheers