first shot is right on,, then others are not ? you cleaned it and you are right on again , well cleaning will not re-zero your scope , and if you don't clean it you just let it cool then your back on zero, right ? not likely or your scope ,your gun would have cooled when you cleaned it bringing you back to zero, the likelyhood the scope would go back to zero after the 3rd shot every time is not likely , if something is loose in your scope it would be all over the place all the time , you might be on zero on your 1st or 5th or 6th and then after it cools be on for your 2nd maybe your zero shot , so I'd bet there is nothing wrong with your scope , as you said fisrt shot is at zero,
however I also agree with the other post that 3 shots should not heat it up to where it is off by 6" maybe 2"
how much wind was there ? again not likely there is only wind after your first shot , but if it is gusting you might be getting lucky on your first shot ,
I'd check the actoin screws , let it cool 5-10min hold/lean on a tree, and again have someone else shoot it
best of luck , lets us know what you find out