All actions lag with Dreamweaver 21 (Mac) using "local" site in networked location

Every action, including focusing back to the window, stalls for anything from 2-10 minutes. A simple text edit on a page took nearly an hour to complete. This has made Dreamweaver 21.0 unusable. The problem does not occur with Dreamweaver 20.2 (although that's pretty laggy too, it's nowhere near as bad).

Note: this is not the typing lag issue mentioned elsewhere.

I checked Activity Monitor while Dreamweaver was running (and lagging) but there was no excessive CPU or memory demand.

I have just one site, with local folders on a networked location (smb share). The remote server is connected in a similar way but at a different location.

I'm running Catalina 10.15.7 on an early 2015 macbook air. There's at least 150GB disk space to spare so it's not that either.

Looking at other issues I might hazard a guess that this has something to do with our local site being at a remote location. I haven't tried moving the local site to a real local location – it's a very old site and will take a long time to do so - I may try that, but even if that solves the problem it won't be a solution as we have several people maintaining this site from different locations.

For now, I will continue to use the older version of Dreamweaver. If anyone has any light to shed on this issue I'd appreciate the help.