Sorry, I don't understand your use case.

Can you please explain ?

ok,

NOTE : below explanation is only happenning when "Automatic run plan" is Checked

i'm selecting the arrow between to activities, i hit the red X to delete the link

it says in a green box, dependency link removed

the and i get this message

2018-11-14 09:46:16.856 ** ERROR ** [V7.2.7] ERROR **
2018-11-14 09:46:16.856 ** ERROR ** [V7.2.7] on file '/var/www/html/model/ProjectMain.php' at line (647)
2018-11-14 09:46:16.856 ** ERROR ** [V7.2.7] cause = Creating default object from empty value.

i'm also getting these error message

2018-11-16 08:34:43.530 ** ERROR ** [V7.2.7] Exception-[42000] SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ') or (successorRefType='' and successorRefId=)' at line 1
2018-11-16 08:34:43.530 ** ERROR ***** [V7.2.7] For query : select count(*) as cpt from dependency where (predecessorRefType='' and predecessorRefId=) or (successorRefType='' and successorRefId=)
2018-11-16 08:34:43.530 ** ERROR ** [V7.2.7] Strack trace :
2018-11-16 08:34:43.530 ** ERROR ** [V7.2.7] #0 Sql->query called at [/var/www/html/model/persistence/SqlElement.php:2465]
2018-11-16 08:34:43.531 ** ERROR ** [V7.2.7] #1 SqlElement->countSqlElementsFromCriteria called at [/var/www/html/model/PlanningElementExtension.php:131]
2018-11-16 08:34:43.531 ** ERROR ** [V7.2.7] #2 PlanningElementExtension->checkDelete called at [/var/www/html/model/Dependency.php:250]
2018-11-16 08:34:43.531 ** ERROR ** [V7.2.7] #3 Dependency->delete called at [/var/www/html/tool/removeDependency.php:48]

2018-11-16 08:37:19.242 ** ERROR ** [V7.2.7] HACK ================================================================
2018-11-16 08:37:19.243 ** ERROR ** [V7.2.7] Try to hack detected
2018-11-16 08:37:19.243 ** ERROR ** [V7.2.7] Source Code = Id 'undefined' is not numeric
2018-11-16 08:37:19.243 ** ERROR ** [V7.2.7] QUERY_STRING = id=undefined
2018-11-16 08:37:19.243 ** ERROR ** [V7.2.7] REMOTE_ADDR = 10.1.120.140
2018-11-16 08:37:19.243 ** ERROR ** [V7.2.7] SCRIPT_FILENAME = /var/www/html/tool/dynamicDialogDependency.php
2018-11-16 08:37:19.243 ** ERROR ** [V7.2.7] REQUEST_URI = /tool/dynamicDialogDependency.php?id=undefined

When i check "Automatic run plan" and i hit "Calculate Activitie planning"

i get this error

2018-11-16 08:52:24.195 ** ERROR ** [V7.2.7] ERROR **
2018-11-16 08:52:24.195 ** ERROR ** [V7.2.7] on file '/var/www/html/model/ProjectMain.php' at line (647)
2018-11-16 08:52:24.195 ** ERROR ***** [V7.2.7] cause = Creating default object from empty value

Hi,

I think your have unconsistency in DB, coming from older patchs on V7.2.
Try and :
- delete all dependecies with non planable items (items that are not displayed standard planning)

If issue still occurs, delete all lines in talbe planningelementextension.

There all should be OK.
Then you can re-create the dependencies.