Optimization results different to single result

[netprofit]

Hi,
i very often have the problem that i get amazing optimization results with some EAs but when i set input parameters i get a much worse result.
Sometimes it seems to be a system , it is about the same factor on each optimization result.
Here: Optimization 402.093 USD, with input paramteters 62.712 USD

Optimization 402.093

result 62.712

I use Ticksotry 1.8.9.5, have ducaskopy data, files are not over 4GB and i cleaned my cache already.
I use fixed spread ...

So i can't use the results. I always need to confirm with a single test
What is the problem.
What can i do ?

It happens time by time with several EAs,

Thanks.

[netprofit]

I think i have found it by myself now:

It is the cache : MT4 ->tester->cache

when i get such strange results and i cleared the cache, it was correct with the second attempt.

So now i clear it after each optimization and it seems to work .

But why ?
What is the problem ?
What can i change for the future ?