One of the most common mistakes that I have heard over the years as an ESL teacher, is the mispronunciation of said.
I suppose it would be logical for the word to be pronounced as 'say-ed', but unfortunately, English is not always a logical language. The correct pronunciation is as follows:
/sɛd/
I know not everyone reads phonetics - basically, it rhymes with the word bed. If you're still not sure about it, you can listen here: https://www.merriam-webster.com/dictionary/said
However, I have to admit that I have occasionally heard native speakers pronounce it incorrectly. I suspect that this is due to some regional dialects.