I'm a programmer and I don't understand what old data could be corrupting the strategy. If the programmer is storing things in a file or in global variables, then yes those need to be cleared.
On the negative TP, I'm sure that problem is because the script is updating TP for trades it should not be ie setting the TP to the TP of trades of different symbols. I've watched it do it, and I've seen it in the logs.
I'm pressed with the EA thus far, but it does need some clean up. If the programmer does not want to do that, I'll update the code fix the TP problem. It is simple of filtering trades by Symbol and hopefully magic number before modifying trades. I'm guessing though once a trade is place the TP should not be modifiied, or atleast till another trade is opened in the same symbol and direction.