Admiral agitator

[SIZE=4]The agitator pops up off its base during the wash and/or rinse cycle. I have pushed it back on numerous times but the issue continue. This has left the clothes still dirty or left with subsantial amounts of detergent left in the clothes. how do I keep this from happening?[/SIZE]

There is a screw under the cap which holds it down. Check to see if this is the problem.