Hey esp, Harrumph is completely correct; it was me who asked this on the Shmups forum. I had the same exact problem. Replacing the fuse F1 fixed my OSSC; D5 was apparently fine in my case, there is supposed to be NO continuity, so yours is probably also fine.
I was only able to get a minimum number of 10 fuses, so I have 9 left. Soldering was not particularly difficult. If you are in Germany, I can send you a few replacement fuses, if you are interested. If you are somewhere else then the postage will probably exceed the cost of ordering them yourself. Let me know.