The 62mm Dexter dust cap, like most dust caps, is a compression fit.
A compression fit means the lip of the dust cap is larger than the hole it fits therefore, it must compress to lock into the hole.
Some 62mm Dexter hubs do not have machined chamfers in the boss and rear of the hub.
Insertion can be difficult. Using a pipe of the correct diameter can greatly improve the ease of which the dust cap can be installed.
Dust cap can become lose if hammered into position too frequently even on the first insert.
Once the dust cap is home, stop hitting it. Extra hit can actually make it loose-fitting.