Conversation exchanges
Most of those problems with unreliable error corrections would of course disappear if you had a native speaker to help you. Luckily, that is nowadays perfectly possible due to conversation exchanges, in which you teach someone your language and they teach you theirs. If you can't find someone locally, there are sites which specialise in setting up international conversation exchanges through Skype, Instant Messenger, etc. As the name suggests, most people mainly want to have the chance to chat in another language through conversation exchanges, and you might not make yourself popular if you expect your (unpaid) partner to correct pages of written work or correct every mistake you make. If it is okay with them, try picking out three or four parts of your written work that you are not sure about or one part of your spoken grammar that you want their feedback on.