You are speaking right out of my head. This is exactly what I'm saying.
Adobe's software is EXPTREMELY poorly programed! No metter what HW you run it on. Every single update makes thing worse and worse. Adobe adds ony tiny new features, but the core frameworks are untouched for ages.
Read this thread, might help to sove your problem:
This is purely my optinion and I cannot prove it by no matters.
But as I see it, Adobe's software programed on non-native Windows and non-native macOS frameworks and runs in some sord of emulation layer on both platforms. This is way it is soo slow, macOS version behaves to tally different to any other macOS native software and so on. There are even bugs in LrC present for +7 years nobody was ever able to fix them.
So I think that it might help, as the bug might be cross platform. Just try it :).
Please post your System Information as Lightroom Classic (LrC) reports it. In LrC click on Help, then System Info, then Copy. Paste that information into a reply. Please present all information from first line down to and including Plug-in Info. Info after Plug-in info can be cut as that is just so much dead space to us non-Techs.