Thank you. The shutter is intermittent. I found during testing that it will actually fire sometimes. Other times, it won't fire and the turn of the film advance crank opens the aperture blades instead. When I depress the shutter release button and let go, it retracts slowly. Definitely seems like lubricants have turned gummy...
Chiming in just for that, not a Rolleiflex but I have a Super Ikonta with a Syncro Compur. That camera has separate winding and cocking with a multiexposure prevention interlock.
My sample seemed CLAd or just well kept (low speeds ok!), came from a dealer but it might have just been shelved by the previous German Owner.
...a couple of months of ownership, and out traveling Xmas in not really cold weather it started doing what your Rollei does.
I noticed that it was the prong of the interlock not springing back after shooting. Cocking it again made the blades to open! ie. it's as if the shutter release is not resetting and stays pressed.
Poking back the interlock solved the issue, but after some exercise with this usual manual intervention during a weekend trip... It now works well! Unfortunately I guess the Rollei does not allow this.
I also played my luck with the self timer, which gave me a scare of a stuck shutter for a bit. So, unless freshly CLAd, might be best not to try that.