Might be me being a bit thick and missing something obvious, My chain is quite slack when the bike is on the side stand, if I move the bike so that the wheel turns 180 degrees it goes quite tight, everything looks OK, both of the adjusters are in exactly the same place by the marks on the swing arm, when moved the chain makes a bit noise as if it is very tight, but feels bit slack.what am I missing.

new chain and probably sprockets time

Tight spot in the chain, basically the chain is shagged

Thought that might be the case but just wanted another opinion cheers