Builder becomes unresponsive when interacting with flow

I’m having an ongoing problem where the builder becomes unresponsive when I try to interact with the ‘Flow’ element. Quite often, when I try to insert a new routine or loop, or click on an existing loop, I see the Mac spinning wheel and Psychopy becomes unresponsive. Sometimes this resolves after 30 seconds or so, sometimes it doesn’t and I have to force quit the software. I’m running Psychopy 2023.1.2 (standalone) on Mac OS Mojave 10.14.6. This doesn’t happen for any other component - only for flow. Any ideas?