MySQL, phpMyAdmin: after insert trigger not firing - mysql

Question

I have defined the following trigger on my database in phpMyAdmin:
It's a very simple trigger where I just insert a record into the history table after an insert in the item table:
insert into history values(null, new.Id, new.LocationId, new.LocationId, new.PersonId, new.PersonId, date(now()))
However, the trigger is not firing (and it worked correctly when I tested it in MySQL Workbench).
Edit 1:
The trigger fires when I define it with some dummy values, like this:
insert into history values(null, 1, 1, 1, 1, 1, date(now()))
Edit 2:
The history table is written into when I define the trigger with dummy values (see edit 1). But the most recently added entry's ID is 11 (ID is auto_increment), even though the last entry before that had ID = 3. My point is that they are not consecutive, but rather as if there were entries in between but were deleted for some reason...
Edit 3:
Here is the DDL for item and history tables:
create table Item
(
Id int not null auto_increment primary key,
InventoryNumber int not null unique,
ItemStatus varchar(20) not null,
ItemType varchar(30) not null,
ItemName varchar(100) not null,
PurchaseDate date not null,
PurchaseValue decimal(12,4) not null,
Amortization decimal(12,4) not null,
LocationId int not null,
PersonId int not null,
foreign key(PersonId) references Person(Id),
foreign key(LocationId) references Location(Id)
);
create table History
(
Id int not null auto_increment primary key,
ItemId int not null,
OldLocationId int not null,
NewLocationId int not null,
OldPersonId int not null,
NewPersonId int not null,
DateOfChange date not null,
foreign key(ItemId) references Item(Id),
foreign key(OldLocationId) references Location(Id),
foreign key(NewLocationId) references Location(Id),
foreign key(OldPersonId) references Person(Id),
foreign key(NewPersonId) references Person(Id)
);
and the trigger (which I think is irrelevant since I didn't import the trigger via a script, I defined it using phpMyAdmin's GUI):
DELIMITER //
CREATE TRIGGER historyTriggerInsert AFTER INSERT ON Item
FOR EACH ROW
BEGIN
insert into History values(null, new.Id, new.LocationId, new.LocationId, new.PersonId, new.PersonId, date(now()));
END;//
DELIMITER ;
And here is another thing I found out: when I add an entry to item using my Yii web application, the entry is visible in the item table in phpMA, but the trigger inserts nothing into the history table. However, when I add an entry to item directly in phpMA, the trigger also creates an entry in history i.e. it works correctly.
Also, when I define the trigger with those dummy values but only leave new.Id, like this:
insert into history values(null, new.Id, 1, 1, 1, 1, date(now()))
it also doesn't work. This and the incrementing ID leads me to a conclusion that the trigger is fired, tries to insert into history, but for some reason gets an invalid new.Id value.