Cannot reproduce (tested on FF and Chrome, both work fine).
Can you detail use case and possibly reproduce on demo ?

Ok, I could reproduce (after a number of retries) on demo project (see attached screen copy that show graphically the link between activities on Gantt view while nothing is persisted in database).
It looks that I had to first assign some time to previous activity to reproduce the problem.

EDIT : I (re)tried to reproduce but did not succeed this time on demo environment. It is though very easy to reproduce on my environment. I noted that my projeqtor environment is way slower than the demo one is (projeqtor installed locally on top of easyPHP). Might be linked ?

Could not reproduce 🙁

I removed all existing dependencies on "testPhase2" sub-tasks, recreated many links (from first to all others, from each to next, ...), also tried to insert assignùent in the mean time.
Never faced an issue.

I also checked log file : no error.

Could you please detail use case step by step to produce issue ?
Also, if you can reproduce, could you please check browser console for errors ?
Thanks

I think I finally understood how to reproduce the problem : it occurs when the "drop" is done on the right of the green rectangle representing the task (on the name of the resource for example). Easy to reproduce especially on "small" tasks.

OK, you got it !!!!

It's not browser dependant (could reproduce on chrome) and not linked to first or second time.
It is just the "drawing" of the dependency line that is active on "resource" area, but drop on that zone does not trigger the insert dependency action.
Will investigate to fix it on next version.Issue recorded as ticket #1802

Thanks for you analysis.