Slightly different shotgun opening issue

[Quixote Kid]

Well neighbors I am new to town and have a shotgun question.
I have a Dakin sxs .20g. Made By Gaspar Arizaga.   The company has mixed reviews.  Dakin's Arizaga family guns get valued anywhere form 50.00 to a couple thousand based on actual sales over the last several years.  Bought new, 20 years in the closet never fired.  Used for the first time in my first match last weekend.  I was stiff to open, but being "new" I expected that. A little polishing; a bottle of oil, a few weeks of playtime with snapcaps and it seemed ready to go.  Well except...
   After firing my primers showed a little extra scratch and I had some difficulty breaking it open so I will be checking the firing pins.
However, my question has to do with the range of motion when it opens.  It easily opens to about 90% (just shy of enough to extract my shells).  If I hold it open it will get me the extra few degrees and I have more than enough room to swap shells. However when I release the pressure it closes slightly and my shells won't pass the edge of the receiver face.  There seems to be some actual spring tension fighting me that last few millimeters.
  I am not sure that it is a malfunction.  I found an article that said some sxs guns have a deliberate feature designed to make it less likely that a hunter walking with his action open would loose his shells if the gun tipped.  
   I am more of a theatrical stage shooter then a speed shooter and will happily "ham" up the requirements of working my guns.  Furthermore I have an emotional attachment to using this piece.  Lost my dad recently and it was his.  Nevertheless if I can safely get the gun to stay open I would prefer it.
Any Ideas?
I'll sure be hopin....

   

[Tascosa Joe]

Spanish shotguns in general are of good to fantastic quality.  My experience has been when trying to make the action open a bit wider may loosen the lock up.