Hadnít seen an update on this lately so I thought maybe you had figured it out.
I didnít suspect you were just waiting for more hair to grow back so you could get back to work on it.
I learned a few things while I was sick with the flu. Electronics and fever are like alcohol and cars and donít mix well. I donít know why I thought an increase in my brain temperature was just as good as an increase in my IQ..... but I did, and I deleted my maps, changed all my settings etc. so what Iím saying is I donít have an answer for your problem but I DO have empathy for the hair pulling part. I quickly learned to just let GSAK
clear the old waypoints before loading the new. Long tech support story from way back but I use com3 on all my PCs. Good luck to both of us.
PS. Will anything else write to your Mag. GPSr, like maps etc. so you can eliminate the GPS and/or SDcard?
PPS. I believe the baud rate for your mag gold should be 9600 but permission denied should have nothing to do with that.
Live a good, honorable life. Then when you get older and think back, you'll enjoy it a second time.