John Cutler
I do not think the posting issue has anything to do with the source. I run an ancient HP PC with Win7, very robust and reliable with no silly bells and whistles.
This morning I posted the problematical article in phases and it worked (In Radio Control: S4 Society Kit Harness). I believe the issue is that the software cannot cope with more than one inserted photo per submission. True? If so, it makes submitting magazine-type articles difficult as you have to post in sequence and hope that no-one interrupts the flow whilst you are in the process!