I would ask if having duplicate plots will affect the chances of winning a block? For example, with 5 PCs(set up as harvesters) in a local network, all the PCS are connected to a main PC. These 5 PCs does plot and share the folders to the main PC. The main PC has all the plots from all these PCs via shared folder, hence, there will be many duplicates since all the pcs are also has these plots farming.
Is this an issue and should I prevent the farming of duplicate plots?
You will get an error in the debug log that lists the duplicate plots. Prior versions could have crashed a harvester if they were there but you get a log error now.