Stephan,
I am sorry but this is not the solution. When you correct the price from 0.6 BTC to 0.5988 BTC then you will be having the same problem next time all over again. Then you need to correct it again and again. It will only go down this way.
The best solution thus far is a little overhead (extra) on both sides of the wallet to compensate for the fee costs.
True, correcting the amount of BTC for the Sell, and not setting it back to 0.6 BTC for the next Buy, (assuming that there is extra in the wallet), would cause the trade amount to continue to go down.
I'm not sure how other exchanges work, but for BTC-e, I think the best solution would be to Sell the trade amount minus the fee (0.5988 BTC in this case), then check the wallet, if there is enough overhead, then leave the trade amount what it was for the next Buy. (6 BTC in this case). If the wallet does not have enough overhead (as a result of negative profit or other reasons), then you will have no choice but to decrease the trade amount (0.5988 BTC in this case).
By the way, if I didn't make it clear, I did have overhead in my wallet when this error occurred. What ever the solution, the bot missing a sell because of an error such as this is a serious problem.
I've finally figured out an Indicator combination that seems to be profitable, but I really don't want to trade with 95% of my wallet, so I will have to wait until you find a solution for this problem before I can continue using the bot.
Thanks,
Darrell