MT4 is in use by 96.4% of retail brokers and obviously any profitable EA or automated strategy is going to impact them individually and collectively (i.e. their liquidity providers). It therefore makes statistical sense for them to automagically 'interfere' with the EA's profitability in much the same way that they spread widen and delay execution during news events. If you can't bring yourself to believe in this chicanery, just go on doing what you're doing and keep complaining here and elsewhere about the poor performance of MDP..... and the magical coincidences of its sudden downturn in performance. This latter isn't something that you can fob off as a function of market volatility - simply because MDP trades often take less than a minute to execute (but are very vulnerable to digital manipulation over that time-span).
No-one said that MT4 isn't a basic 'good platform'. It's just that it, and in particular, its free data-feed is everywhere the choice of us dumb-asses - and it's precisely that fact that makes us very vulnerable to brokers doing whatever they like to us - with the complicity of the MT4 creator, the House of Metaquotes. Together they make quite an evil cartel that's not unlike any casino that modifies their roulette wheels to favour the house. Brokers love losers.