This issue results from the Ketra A20 bulb maxing out the depth of the socket. In some cases, the bulb does not seat properly and is unable to be secured sufficiently by the threading in the socket due to differences in size of the soldered contact point on the bulb.
Possible Solutions:
1) For table lamps, unplug the table lamp and pull the metal tab out.
2) File the silver tip down on the A20 bulb (may be used for all fixture applications).
This image features (3) Ketra bulbs all with varying soldered contact sizes.
This image features (3) Ketra bulbs and (1) NICHE bulb for comparison of the soldered contact points.
