There are some- the same suffix can have two spellings: -or or -er. However, while 'cooker' is the machine, not the peson, there aren't that many examples. -ed could be the past tense or the past participle of a regular verb, but context would enable the learner to distinguish. There are also those adjectives that appear to have the adverb suffix -ly, like 'lovely'. Most areas where there is confusion, there are resources- such things are frequently covered in books.
If you look at our Quizzes section, you'l find quite a few exercises covering these areas.
- For Teachers