Unable to extrude SubD face(s)

I’ve been building (and extruding) a subD model in Rhino7 from a subD cylinder. After editing, deleting and bridging my low poly mesh back to a closed subD object, I am getting issues with extruding faces. I created a new cylinder portion to match the subD object I am working on and am still unable to extrude faces off of this one as well!

Creating a cube or cylinder primitive in the same model works just fine when extruding faces.

I have run the repairSubD command but there were no issues reported.

Working on the latest build of Rh7 and have rebooted my machine and imported the mesh into a new scene, but still no joy.

Have run Edge Tools and Diagnostics on the mesh, but nothing is reported.

Just wondering if anyone has come across a similar issue?

PS I can see the wire-frame extrude happening when I pull it, but as soon as I hit Enter, the face remains unchanged!

Hi - Can you post an example file and a detailed description of what you are doing?

Hi Wim, yes for sure. I have attached it.
Seat_Control_pod_18_05_21_02.3dm (2.1 MB)
I have rebuilt the mesh on Default Layer - the original is on the Version 4 layer

I am working with Reflect SubD on and I have just discovered that extruding faces on the Greyed out half of the model (i.e. the instanced reflected side), then extrude Faces does not work, but if I extrude faces on the non instanced side, then everything works.

The new mesh created on Default layer, has the two hemispheres clearly indicated, but the Version 4 I have been modeling on, seems to have lost the distinct grey split colouring(even after resetting the Reflect axes), which is where I got mixed up.

Not sure if this is a bug!