The issue:
Open a fresh project in Reaper (latest release v 5.70 64-bit).
Add a new track.
Open FX and insert a Silent Way plugin, e.g. SW LFO. The plugin works.
Try to add another SW plugin, e.g. SW ESX-8CV Combiner OR try to remove the first SW plugin.
Nothing happens. Beach ball spins. Need to Force Quit Reaper.
I haven't tested all plugins, but all that I've tested cause the hang.
No other plugins (only SW) I've tested cause this issue.
I googled and searched here, but came up empty.
FWIW, I have Ableton, but only the Live Lite version. I don't use it much, but Silent Way plugins seem to load OK there, even more than one, though unloading them takes longer than I would expect - beach balls briefly but eventually proceeds without hanging the whole program. So maybe it's more a Reaper issue than SW, but since other plugins aren't causing me problems I figured I'd start here.
EDIT: Actually, putting 2 SW plugins into a Live set, e.g. LFO and CV to MIDI, and then trying to close that set causes a hang as well. . . .

Thanks for any input. Happy to troubleshoot in any way.