If you meant it fired twice with one pull of the trigger, I'd get that trigger group out of that rifle immediately if not sooner.
I'd also give it to someone else to store, or send it off for repair, or disassemble it into parts.
Not exactly what you meant by "double feed", but.........
Just a bit of over cautiousness. I too have had some rifles with questionable triggers, but I "tag" it (with an AMTRAC luggage tag) and note it on my rifle ID card. Some I've fixed, some had Murray or Kavarri work.
On all "new-to-me" SKSs I do the sear drop/bang test after a thorough cleaning and before any range trip.
I learned the hard way.
My third or fourth SKS, (& my first Paratrooper) I was at the range for the first time with the Para, another newly acquired SKS and my nephew. All was going smoothly when we switched guns. I was running the Para for the first go, both new guns freshly cleaned, free firing pin bolt rattle. My nephew babied the Para into battery and the bolt didn't close, and it didn't fire when he pulled the trigger. I said "STOP, put the safety on, point it up", cleared my gun and had him hand the Para to me. I said you gotta let the bolt fly, then went to clear the round and when I touched the carrier, the hammer flew (sear fail), a round went off, blew a hole in the roof, cycled another round, and the bolt handle ripped my palm open. The range was hot and the closest shooter was 4 stalls over, so nobody paid any attention. That was 11 years and 36 SKSs ago. PAX