@Andreas – thank you for letting me know. Yes, that it must be incredibly frustrating for TalkPhysics to waste your time and effort like that. I’ve particularly appreciated how much you’ve contributed recently!
@Ian – thanks for confirming.
I haven’t seen this problem before, so I need try and replicate it. Can either of you make it happen “on demand”? Please feel free to do that replying to this post, or use the “Trying Out TalkPhysics” group – https://www.talkphysics.org/groups/540 . Which browsers, version and operating systems are you using? Is it always after using the “preview”? Thank you for any help you can offer.