Hi,
I have an error when i create a new item with screen customization plugin but nothing is logged in .log
Here is the .log file :
2016-12-09 09:08:11.192 ===== TRACE ===== NEW CONNECTED USER 'ldumas'
2016-12-09 09:39:51.588 ===== TRACE ===== DISCONNECTED USER 'ldumas'
2016-12-09 09:39:52.295 ===== TRACE ===== NEW CONNECTED USER 'ldumas' (using remember me feature)
2016-12-09 09:43:00.461 ===== TRACE ===== New plugin found : screenCustomization_V2.1.zip
2016-12-09 09:43:00.484 ===== TRACE ===== Plugin unzipped succefully
2016-12-09 09:43:00.492 ===== TRACE ===== Plugin descriptor information :
2016-12-09 09:43:00.492 ===== TRACE ===== => name : screenCustomization
2016-12-09 09:43:00.492 ===== TRACE ===== => description : Customization of screens
2016-12-09 09:43:00.492 ===== TRACE ===== => version : 2.1
2016-12-09 09:43:00.492 ===== TRACE ===== => compatibility : V5.2.3
2016-12-09 09:43:00.493 ===== TRACE ===== =====================================
2016-12-09 09:43:00.493 ===== TRACE =====
2016-12-09 09:43:00.493 ===== TRACE ===== PLUGIN SQL FILE : ../plugin/screenCustomization/screenCustomization.sql
2016-12-09 09:43:00.493 ===== TRACE =====
2016-12-09 09:43:00.494 ===== TRACE ===== 1 lines inserted into table "menu".
2016-12-09 09:43:00.515 ===== TRACE ===== 1 lines inserted into table "habilitation".
2016-12-09 09:43:00.519 ===== TRACE ===== Table "plgcustomlist" created.
2016-12-09 09:43:00.522 ===== TRACE ===== Index "plgcustomlistScope" created.
2016-12-09 09:43:00.522 ===== TRACE =====
2016-12-09 09:43:00.522 ===== TRACE ===== DATABASE UPDATED
2016-12-09 09:43:00.522 ===== TRACE ===== WITH NO ERROR
2016-12-09 09:43:00.522 ===== TRACE =====
2016-12-09 09:43:00.522 ===== TRACE ===== Plugin updated database with 0 errors from script ../plugin/screenCustomization/screenCustomization.sql
2016-12-09 09:43:00.612 ===== TRACE ===== Plugin screenCustomization V2.1 completely deployed
2016-12-09 10:05:07.221 ===== TRACE ===== =====================================
2016-12-09 10:05:07.221 ===== TRACE =====
2016-12-09 10:05:07.221 ===== TRACE ===== PLUGIN SQL FILE : ../plugin/screenCustomization/temp.sql
2016-12-09 10:05:07.221 ===== TRACE =====
2016-12-09 10:05:07.228 ===== TRACE ===== Table "client" altered.
2016-12-09 10:05:07.228 ===== TRACE =====
2016-12-09 10:05:07.228 ===== TRACE ===== DATABASE UPDATED
2016-12-09 10:05:07.228 ===== TRACE ===== WITH NO ERROR
2016-12-09 10:05:07.228 ===== TRACE =====
And here is the dialog error :

Add : I have the same error when i want to delete a created item (because sometimes i can create items....)
After many tries i'm still in trouble, i found that it seems to work fine on all tables EXCEPT clients (i started with clients), here is the log from developper tools (chrome)

Your print screen confirms issue with Client class.
Please post here projeqtor/model/custom/Client.php for us to analyse.