After upgrade, UI stuck at "Adding flows to workspace"

Hello together,

I am not sure if this is really related. I suddenly have the same "Adding flows to workspace" problem, but with a different error and on Windows 10 (Chrome as well as Firefox):


It came out of nothing. Yesterday all was fine, today this, without updating node.js or Node-RED.
I did, however, update both to the latest stable versions after encountering the blocker. my status now:

23 Jul 11:48:52 - [info] Node-RED version: v1.1.2
23 Jul 11:48:52 - [info] Node.js  version: v12.18.3
23 Jul 11:48:52 - [info] Windows_NT 10.0.19041 x64 LE
23 Jul 11:48:52 - [info] Loading palette nodes
23 Jul 11:48:53 - [info] Dashboard version 2.23.0 started at /ui

Any ideas?