The issues you mention are mostly the trading platform dependent. When you are choosing a reputed trading platform, you will not face any issues.
Not in bitcoin trading, but in my Forex trading I have faced the many issues like order is not getting executed and not connecting to live market are some of major issues, I have faced in my trading.
Well said and thanks for clearing that out. I think I forgot to tell the thing is altcoin to bitcoin and vice versa.
How about the live markets with different prices? How do you deal with it? Are you picking a website that sells it way cheaper even if it is not that reputable?