If your puzzle solving methods were completely valid, your calculation and pattern recognition skills would be over the roof. Clearly they aren't seen in your games, which leads me to
Conclusion #1: You are a sandbagger and you are purposefully playing bad. This is very unlikely, as someone with such a strong puzzle rating like you would 100% have a title.
Conclusion #2: You are allowing someone else much worse to play on your account which is affecting your live rating. Again, this is very unlikely as your account would be banned.
Conclusion #3: You are using an engine for puzzle completion. You want attention for being such a great puzzle solver even though your actual rating and puzzle comprehension is quite low. This is the most likely scenario.
Your puzzle rating a year ago more accurately represented your actual rating. I'm guessing since then you started using an engine for puzzle completion.