Yes all objects (spawner and spawn) have the recoverable: false setting. I only added the fixedweapon entry to make EXTRA sure.
I am using my own personal mod and sadly i do not have a savegame.
The bug is VERY elusive as you need an auto-recovery for it to make it appear, sorry about that.
Somewhat related:
If you make an equippable tank and give it on a mission e.g a auto-cannon with e.g incendiary rounds loaded and return with 3 (or X) shots of 6 left, you will receive 3 (or X) full clips of whatever ammo is listed FIRST in the items section of your auto-cannon, not necessary the incendiary ammo, but the FIRST entry. I have to admit I abused that recently by starting with a weapon i only had one clip for and farmed/harvested the free ammo then...
Those are not really dreadful bugs, but I wanted to contribute a bit to your excellent(what an understatement) work.
And yes I know it isn't that difficult to upgrade, but I am very LAZY atm...