The bases were originally designed for compact fluorescent lamps.
The issues you describe arise from the difference between the two
compact fluorescent designs.
The G24d based CFL lamps (which only have 2 pins coming out of the
bottom of the base have a starter in that square post that extends down
between the pins. That was the original design. The G24q based CFL
lamps were designed for newer electronic and/or dimming ballasts which
have a different starting circuit. The two circuits are not really
compatible and the base/socket "fit" was designed to prevent improper
insertion of the 2 pin G24d base into the 4 pin G24q socket by making
the "post hole" in the G24q socket shallower.
Apparently the LED lamp you purchased was designed to fit the G24q
Post by charles
I have some G24 LED lamps, and have a problem with two types of
sockets, the socket is not deep enough for the bulb to seat.
The bulbs are G24D, the sockets are G24Q , if that makes any
difference. One batch of sockets had a small post inside which I
could break off to allow the bulb to seat, the other socket wasn't so
easily modifiable. The tail on the bulb measures about 22.5 mm. I
cut the tail back to 18.5 mm and it works with the sockets.
Do I have bad bulbs, sockets, or luck? Is there some standard
dimension for this portion of the bulb?