Car Slowed Down On Its Own problems of the 2008 Nissan Altima Hybrid

Traveling south interstate 95 passing lane on curve @ east lyme CT. Car suddenly decelerated rapidly. Accelerator would not respond to depression. I couldn't immediately coast into right lane & no breakdown lane on my side. Cars behind me, apparently because there were no brake lights activated, drove right to my bumper & began honking. When surprisingly the accelerator responded from complete halt , right lane cleared and I moved through it immediately onto exit ramp. I was baffled & car was responding so I rounded into east lyme stop & shop parking lot with blinkers on. After composing myself, I continued home on back road without incident. Two weeks later leaving my development the vehicle was traveling at 30 (slight uphill) and same thing happened with my wife present; vehicle behind was alerted by hand signals to pass. After accelerator recovered function within minutes (slower than previous incident) I contacted Nissan repair grossman's old saybrook from home. They said to bring it in. I said is it safe? they said I could contact aaa. I called a friend with a diagnostic computer which indicated a "transmission module" failure. Then, at Nissan, shop foreman claimed that since there was no dash indicator or trouble code with his device there was nothing they could do. 1/4 mile away, the car stalled in middle of large intersection making a turn blocking everyone. When it recovered, I returned and he again claimed there was nothing they could do and kept asking me where I bought it. I told him it was unsafe to drive, until a mechanic overheard and convinced him to allow investigation. Mechanic acknowledged code. Test drive nothing happened. Shop foreman refused to note "accelerator failure" & wrote power failure. They ridiculed when told online search "accelerator failure" gets hits. Shop has it since September 15th to date without notice? options?.