It’s happening with a cloned swimlane diagram or a new one created from template.
Tested in both Chrome and Edge, same problem.
@MarkHewitt -
Is this happening in just one board? Can you try creating a new test board with a bare bones swimlane diagram with three activity boxes and see if the behavior is reproducible there?
Kiron
I can confirm the exact same behavior started happening to me today with one swimlane diagram that I’ve been building.
One workaround I found so far was to drag the arrow from one of the boxes inside of the diagram to an empty space outside of the diagram. this will cause the arrow to not disappear. Then drag the arrow to the desired place inside your diagram and it will remain there. This workaround is allowing me to proceed with my work but it is rather annoying.
Sounds like it might be a bug then, @Bruno Filipe Ferreira Soares and @MarkHewitt.
One of you might want to open a support request with Miro to investigate this further: Submit a request – Miro Support & Help Center
Kiron
Yes, same things happening now for me even tho I am making from the template of swimlanes with connection lines...
Created a brand new board, added a swimlane diagram and it still happens.
It seems to be any table, whether created by a template or not. Have opened a bug here:
https://help.miro.com/hc/en-us/requests/495843
Okay, apparently it’s known and they’re working on it:
Hey Mark,
Thank you for the report!
I'm afraid that currently, there's a bug on our end that causes this behavior. The good news is that the team is already aware of the issue and is currently working on a fix for it. We're bringing our sincere apologies for all the inconvenience it causes!
We'll definitely keep you updated on the progress. Please, bear with us!
Warm regards,
Alyona
Miro
Hello Mark
I am having the same issue. Do you have any idea when this will be resolved?
Thanks a lot!
Olivier
Hello Mark
I am having the same issue. Do you have any idea when this will be resolved?
Thanks a lot!
Olivier
Hi Oliver, as you’ll see above it’s a known bug and they’re working on it, beyond that I know as much as you do 
I don’t know if they’ll close my bug (linked above) when they resolve it but it might be worth watching that.
I followed @Bruno Filipe Ferreira Soares suggestion and duplicated existing arrows from the board and that worked. Thanks, it was driving me nuts!!
Same thing happening to me. Jean’s workaround is effective, but I hope they fix it soon
I followed @Bruno Filipe Ferreira Soares suggestion and duplicated existing arrows from the board and that worked. Thanks, it was driving me nuts!!
Same thing here 
. Hope there’s a fix soon
Please +1 me when this is fixed
+1 would like to know when this is fixed.
Notified by the dev team that this issue has now been resolved, I’ve tested it and it works fine for me.
It seems to be any table, whether created by a template or not. Have opened a bug here:
https://help.miro.com/hc/en-us/requests/495843
The above link points to nowhere. Is this issue resolved ? I am still facing the issue with connecting lines getting distorted in a swimlane diagram.
I’ve recently started seeing this issue when drawing lines between AWS objects. If you try to draw a line from one AWS shape to another the line immediately disappears. Am seeing the issue across multiple boards. The issue only seems to occur when trying to add shapes/lines within AWS Groups.
