Ive added some more to my post but I have a similar experience to you. There are words which I've listed in my post which I am more likely to stutter on but I could say them perfectly fine for a whole week and stutter on something else and then it'll change eventually. Some weeks I can't say a sentence without stuttering and that usually gets my heart pumping which makes it worse. Its rare that happens but frightening when it does happen. Another word I struggle with is "clinic" I can't get the start of it sometimes and sounds like jibberish. Another is "prescription" which I struggle to say and I don't know if it's as simple as I can't say it due to my stutter or it's a word I struggle to say as if I was a 3 year old. There is another phrase I also struggle with in work which is "can I take your name please and I'll let the caller know your on the line" it'd the last part I struggle with