Weird 80mm planar issue?

[Softbox]

So, yesterday my mint 80mm f2.8 planar non-T* threw me a curve ball.

Everything was working perfectly, and all of a sudden the normal mechanical behavior of the lens "reversed." It would seem the lens "fires" upon the RELEASE of the shutter button instead of instantly.

Here's what's supposed to happen:
-Press shutter button
-Lens stops down to set aperture
-After set shutter speed length, lens shutter closes
-Let go of shutter
-Rear shutter in body closes

Here's what it's doing:
-Press shutter button
-lens shutter closes immediately
-let go of shutter button (slowly)
-lens shutter opens, stops down to set aperture
-rear shutter in body closes (split second after exposure, not long enough for proper exposure)

Anyone ever seen this?? It's not my 500cm body. My other lenses work fine.
I'm baffled.

 

[polypal]

How about some TLC like a full service and a new mainspring?

Keep in mind this lens is part of a mechanical system that needs to be serviced every 3-5 years to keep up performance.

 

[Softbox]

That's very possible (although I recall this particular lens having been serviced not too long ago).

I'm just curious if anyone has ever seen a problem like this. I sure haven't. Most of my lenses that needed service just had sluggish slow shutter speeds and the like.

 

[polypal]

Broken leaves from shutter or aperture, seized helicoids are other misfortunes that can happen.
Lenses that receive a regular professional service are not very likely to fail.